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Optical multi-band (OMB) systems exploit the low-loss spectrum of the single mode fiber (SMF) and are key enablers to increase the transportation capacity and node connectivity of already deployed systems. The realization of OMB systems is mainly based on the technological advances on the component and system level, and for this purpose, a broad gamut of various structural elements, such as transceivers, amplifiers, filters, etc. have been commercialized already or are close to commercialization. This wide range of options, which aid in unlocking the concurrent transmission in all amplification bands, is reviewed here for the first time, whilst their pros and cons as well as their limitations are discussed. Furthermore, the needs for additional components in order to fully exploit the -390 nm low-loss wavelength range of SMF, which spans from 1260 to 1650 nm, are highlighted. Finally, based on a physical layer formalism, which incorporates the impact of the most important physical layer constraints for an OMB system, the attainable capacity and transparent reach of each amplification band are quantified. [ABSTRACT FROM AUTHOR]

This paper investigates for rising optical fiber transmission strength, increasing bandwidth, and decreasing communication system weakness by using wavelength division multiplexing (WDM). WDM gives today's distention speed and communication traffic. Systems using WDM faces nonlinearities, which the most intensive nonlinear attack is, four wave mixing (FWM). FWM creates and increases crosstalk between WDM channels as a result slows down and impairs the performance of the communication system. This investigation uses orthogonal frequency division multiplexing (OFDM) for evaluating execution of WDM fiber system by repairing Polarization Mode Dispersion (PMD). We took results in the case of trying PMD-Emulator and without trying PMD-Emulator in the system design. We compared the results got in both cases. Furthermore, we compared the performance of the system with the investigations done using different ways, methods, and techniques for compensating PMD and FWM appears in WDM systems. As PMD-Emulator, helps enhancing the system design performance, and OFDM gives the feature of robustness and useful execution to the system. OFDM examined by appointing interfered orthogonal signal sets, for 16 channels; with equally spaced OFDM channels. Oure results showed that the optical fiber communication system using OFDM technique gives perfect removing FWM signal crosstalk, and accurate data transmission, comparing to other techniques used in other researches. We got a decreased FWM power to -77dBm, and the BER of -0.317. Furthermore, the system quality increased with applying PMD-Emulator and OFDM. In addition, using PMD-Emulator in the system design raised the results effectiveness. The program used in the present work is optisystem-15, and the results obtained in this study coincide with the theoretical and actual results obtained by the previous studies. [ABSTRACT FROM AUTHOR]

At present days, metropolitan and access communication networks are markedly developing utilizing a variety of technologies. Their bearer communication infrastructures will be mostly exploiting the optical transmission medium where wavelength division multiplexing techniques will play a key role. Wavelength-Division Multiplexed Passive Optical Networks (WDM-PON) attract considerable attention for the next generation optical metropolitan and access networked systems. Simultaneously, the utilization of common optical network resources in wavelength domains will be more important. The main purpose of this paper is presented by the evaluation of resource efficiencies for the non-symmetric dynamic wavelength allocation method applied in the WDM-PON network design with a conventional topology. This contribution introduces a novel non-symmetric Dynamic Wavelength Allocation (DWA) method for a selected network design with the utilization only passive optical splitters in remote nodes. This novel wavelength allocation method is oriented on minimizing a number of working wavelengths that will be used for compliance of customers' requests for data transmitting in the common point-to-multipoint WDM–PON network design. For evaluation of wavelength scheduling, a simulation model related to the conventional WDM-PON network design is realized in the MATLAB programming environment is presented with results. Finally, different traffic loading scenarios are determined and, subsequently, resource efficiencies of the presented non-symmetric DWA method are evaluated from a viewpoint of application in future WDM-PON network designs. [ABSTRACT FROM AUTHOR]

The transfer and synchronization of high-precision frequency are crucial for various application fields. Recently, the fiber link has become an attractive option for long-haul frequency dissemination. In this paper, we demonstrate a stable radio-frequency (RF) fiber-based transmission system with passive compensation method by frequency mixing. Different from previous solutions, single wavelength of the optical carriers is employed in the proposed system to maintain the transmission symmetry. The frequency-tripled signal at the local end is utilized to avoid the effects of backward Rayleigh scattering and mitigate the interference from the phase-conjugated signal. Additionally, instead of tracking the phase drift of the fiber link like an active compensation, the remote reconstruction module based on phase-lock-loop (PLL) is used to improve the transfer performance in our passive scheme. In the proof experiment, the transfer stabilities of the implemented system are 2.86 × 10−14/1 s and 6.62 × 10−17/10 4 s over 80 km standard single mode fiber link. [ABSTRACT FROM AUTHOR]

We report the results of a study of the optical gain properties of binary blend films of regioregular poly(3-hexylthiophene) (RR-P3HT) and poly(9,9-dioctylfluorene-co-benzothiadiazole) (F8BT). Efficient optical gain is observed in the 10-20 wt. % RR-P3HT composition range and can be tuned to the ∼650 nm window utilised for polymer optical fibre data-communications, with maximum gain ∼50 cm-1. At higher P3HT fractions, gain thresholds increase substantially, consistent with the observed concomitant improvement in photocharge generation. Distributed feed back lasers with one-dimensional gratings exhibit pump pulse thresholds as low as 8 nJ (26 μJ cm-2, 2.17 kW cm-2), lower than many other polymer-based gain media in this wavelength range. They also provide relatively high slope efficiencies >2%. The confluence of efficient optical gain with electronic properties that are conducive to charge carrier injection and transport is relatively novel and is expected to be a necessary requirement for the achievement of electrically pumped lasing. [ABSTRACT FROM AUTHOR]

We fabricate double-tapered optical fibre tips by the interfacial layer etching method. The optical fibre is first etched by means of meniscus-based etching to obtain one-tapered fibre tip, which is etched again by the interfacial layer between the etchant and the overlay to obtain a double-tapered tip. The formation mechanism of the second taper is analysed. The impacts of the interfacial layer etching time, HF concentration and the overlay on the second cone angle are discussed. The second cone angle can be controlled by the interfacial layer etching time and the overlay. But the HF concentration has few impacts on the second cone angle. The double-tapered fibre tips can be applied for the contactless trapping of particles. [ABSTRACT FROM AUTHOR]

In order to separate the multiplexed beams with different wavelengths in an all-fiber network, a novel concept of distinguishing different wavelengths by the orbital angular momentum (OAM) beams [i.e., L(topological charge) =1 and $L=-1$ ] based on the OAM fiber is proposed and investigated in the theory and experiments. Meanwhile, a new OAM fiber supporting the first order vector modes (i.e., TE0,1, HE2,1, and TM0,1) is also designed and fabricated. For the sake of verifying the feasibility of the proposed scheme, an experimental platform is anticipated and established. Bit error rates (BERs) and constellation diagrams are employed to evaluate the performance of the proposed schemes with respect to the transmission rate of data (V) and the difference of wavelength between the two input lasers. The simulated and measured results demonstrate that two different wavelengths (i.e., 1548 and 1545 nm) with the cycle of 14 and 10 nm can be distinguished though two OAM beams (i.e., $L=1$ and $L=-1$), respectively. The measured BERs and constellation diagrams with respect to data rates (V) depict that the performance of the proposed schemes degenerates with the increment of data rates (V) from 5 to 40 Gb/s. Similarly, the measured BERs and constellation diagrams with respect to the difference of wavelengths also demonstrate that the performance of the proposed scheme can be improved by increasing the difference of wavelengths from 1 to 4 nm. [ABSTRACT FROM AUTHOR]

The phenomenon of modal noise, which is typically undesired within fiber optic links, is exploited advantageously to characterize vertical cavity surface emitting lasers (VCSELs) operating in the first optical window (wavelength $\lambda \simeq 850$ nm), in terms of frequency chirping. The proposed method, which can be applied utilizing ordinary laboratory components and instrumentation, contributes to fill an existing gap. Indeed, the methods which are typically exploited to determine this undesired optical frequency modulation can be straightforwardly applied only to sources operating at wavelengths of 1310 and 1550 nm, while they become unpractical or even inapplicable at wavelengths of 850 nm. Through the proposed technique, the evaluation of chirp coefficient $M$ and phase difference $\psi $ between frequency and intensity modulation (or equivalently linewidth enhancement factor $\alpha $ and chirp scaling factor $\kappa $) of VCSELs can be performed. This allows the correct design of various types of fiber optic links, making possible to take advantage of these low-cost and low-consumption optical sources. [ABSTRACT FROM AUTHOR]

In this paper, we propose and experimentally demonstrate a tunable erbium-doped fiber laser (EDFL) with Sagnac interference loop with 45° angle shift spliced polarization maintaining fibers (PMFs). In the Sagnac loop, two PMFs with similar lengths. The Sagnac loop outputs a relatively complex interference spectrum since two beams transmitted in clockwise and counterclockwise encounter at the 3 dB coupler, interfere, and form two interference combs when the light transmitted in the Sagnac loop. The laser will excite and be stable when two interference lines in these two interference combs overlap together. Then by adjusting the polarization controller, the wide wavelength tuning is realized. Experimental results show that stable single wavelength laser can be realized in the wavelength range of 1585 nm–1604 nm under the pump power 157.1 mW. The side-mode suppression ratio is not less than 53.9 dB. The peak power fluctuation is less than 0.29 dB within 30 min monitor time and the side-mode suppression ratio is great than 57.49 dB when the pump power is to 222.7 mW. [ABSTRACT FROM AUTHOR]

A novel design of a polarization filter based on photonic crystal fiber (PCF) is proposed in this paper. With the introduction of a gold-coated air hole, the resonance strength is much stronger in y-polarized direction than in x-polarized direction at some particular wavelengths, which is due to the metal surface plasmon effects. At the wavelength of 1.31 μm, the loss of y-polarized mode is 2138.34 dB/cm while the loss is very low in x polarization. Furthermore, the loss peak can be flexibly adjusted from the wavelength of 1.26 to 1.56 μm by changing the thickness of a gold layer, and the loss in y polarization can be kept above 1200 dB/cm. The significant loss in y polarization makes this PCF a good candidate for developing a polarization filter with high performance. [ABSTRACT FROM AUTHOR]

Over the past several decades, the data-carrying capacity of a single optical fiber have been increased significantly by fully exploring and optimizing physical dimensions of the light. Generally there are five major candidates of dimensions, including time, wavelength, polarization, space and quadrature (phase and amplitude). Multi-dimension, utilizing more than two dimensions of the light simultaneously, is one of the essential characteristics of next generation optical communication systems. We review recent advances in transmission of multi-dimensional signals, and highlight innovative ways of exploring the polarization dimension to further increase the capacity or spectral efficiency of a single optical fiber, a so-called pseudo-polarization-division-multiplexing (PPDM) technique. Related demonstrations include non-orthogonal PDM, PPDM of three and four states (PPDM-3 and PPDM-4). Brief discussions on trends of multi-dimensional signal transmission technologies are also presented. [ABSTRACT FROM AUTHOR]

The results of international comparisons in the field of fiber-optic communication and information transmission systems, in particular, for the average power of optical radiation (COOMET PR-S6 and APMP PR-S2 projects) and chromatic dispersion in an optical fiber (EURAMET PR-S3 project), are considered. Data on comparisons as regards the length of the optical fiber (APMP PR-S8), polarization mode dispersion (COOMET PR-S9 project), and wavelength for fiber optics (COOMET PR-S8 project), all of which are now being performed, are presented. [ABSTRACT FROM AUTHOR]

We report a large mode area (LMA), Ge11.5As24Se64.5 six-fold symmetry quasi-periodic dual cladding leakage channel fiber (LCF) for supercontinuum generation (SCG) from 2 to 15~\mu \textm wavelengths. The proposed LMA fiber exhibits single-mode behavior by means of higher order mode delocalization for the entire wavelengths. Besides, the LCF possesses two zero dispersion wavelengths at 4.36 and 14.16~\mu \textm . Indeed, we numerically demonstrated the spectral broadening of continuum for the first time from 2 to 15~\mu \textm in the quasi-periodic dual cladding LCF for a length of 10 mm. It is observed that the red-shifted soliton at the centre wavelength of 9.42~\mu \textm obtain an energy of 0.164 nJ for a low input energy of 0.2 nJ. Further, the SCG in the proposed LCF attains a high conversion efficiency of 82 % at the solitonic spectrum and broadest spanning from 2 to 15~\mu \textm for the low input energy of 0.2 nJ. Thus, the proposed LCF-based SC source is the best choice for the applications, such as optical sensing, optical communication, food quality monitoring, and early cancer diagnostics. [ABSTRACT FROM PUBLISHER]

A mode-forming remote switch in multi-mode fiber distributing networks has been proposed. It can transmit the desired data to the desired port by adjusting transmitter signals. Feasibilities of the proposed scheme are confirmed by switching sub-carrier BPSK signal to the selected port. A graded-index multi-mode fiber link whose output is divided into two ports by a mode-dependent optical coupler, is used as mode-division multiplexing network. Its channel matrix is obtained by using MIMO processing technologies. Amplitudes and phases of the data are adjusted according to the channel matrix. The data is successfully switched to the desired port. Also, wavelength independences are clarified. [ABSTRACT FROM AUTHOR]

We propose and demonstrate a multi-channel SPR sensor based on the cascade application of the single-mode and multimode optical fiber. At this article, we studied the relationship between the gold film thickness and the sensing performance of the multimode fiber-based SPR sensor, the larger is the gold film thickness, the longer is the resonance wavelength, and the better is the sensitivity. We also studied the relationship between the grinding angle of the single mode optical fiber and the sensing performance of the single mode fiber-based SPR sensor, the larger is the grinding angle, the longer is the resonance wavelength, and the better is the sensitivity. Based on the above research, the reflected light of the single mode fiber-based SPR sensor is injected into the multimode fiber, and the multi-channel fiber-based SPR sensor is realized by fabricating transmitted SPR sensor on the multimode fiber. We realize the designable dynamic range adjustment by the cascade application of the single-mode and multimode optical fiber, and the sensitivity keeps constant. When the thickness of the gold film on the multimode fiber is 35 nm and the grinding angle of the single mode fiber is 16°(the gold film on the single mode fiber has a fixed thickness of 50 nm), the sensitivity of the two sensing zone on the multi-channel SPR sensor reach 2115 nm/RIU and 5212 nm/RIU respectively. [ABSTRACT FROM AUTHOR]

A long-range hybrid slot surface plasmon waveguiding structure that is capable of achieving ultra-small mode confinement and a long propagation distance simultaneously is proposed in this article. In comparison with the conventional long-range hybrid surface plasmon waveguide, the proposed waveguide can provide one order smaller mode area and a longer propagation distance by introducing a through-slot in the gap region. Meanwhile, the practical fabrication errors have little influence over mode properties of the waveguide. These results indicate that our designed waveguide can be a potential candidate for high-performance nanophotonic circuit and device. [ABSTRACT FROM AUTHOR]

We studied the reflection spectra of one-dimensional deformed periodic photonic crystal at the optical telecommunication frequency range, using the theoretical model based on the transfer matrix method. A broad reflection bands covering the 1.3 and 1.55 $$\upmu$$ m wavelength of telecommunication was obtained. The propagation of signals is forbidden for all incident angles and for both transverse electric and transverse magnetic polarizations. The deformation of the stack was introduced according to a power law with a coefficient k that represents the deformation degree. [ABSTRACT FROM AUTHOR]

A mathematical framework is presented to study the evolution of multi-point cumulants in nonlinear dispersive partial differential equations with random input data, based on the theory of weak wave turbulence (WWT). This framework is used to explain how energy is distributed among Fourier modes in the nonlinear Schrödinger equation. This is achieved by considering interactions among four Fourier modes and studying the role of the resonant, non-resonant, and trivial quartets in the dynamics. As an application, a power spectral density is suggested for calculating the interference power in dense wavelength-division multiplexed optical systems, based on the kinetic equation of the WWT. This power spectrum, termed the Kolmogorov-Zakharov (KZ) model, results in a better estimate of the signal spectrum in optical fiber, compared with the so-called Gaussian noise model. The KZ model is generalized to non-stationary inputs and multi-span optical systems. [ABSTRACT FROM PUBLISHER]

We propose and demonstrate a reflective-distributed surface plasmon resonance (SPR) sensor based on the twin-core fiber. Firstly, we study the effects of the fiber dual tapered (DT) probe grinding angle on the SPR dynamic range. The results show that for larger grinding angles, the resonance wavelength increases, resulting in a higher testing sensitivity. By using this method, we can make the sensor operate in an optimal waveband. Secondly, on the basis of the results above, we grind the DT probe to be an asymmetric wedge shape to configure two grinding angles (6° and 17°) to realize the distributed sensing. Results show that, with the refractive index detecting a range of 1.333–1.385, we can get two separated sensing zones, 591–715 nm and 729–966 nm, the testing sensitivity are 2385 nm/RIU and 4558 nm/RIU respectively. By using this method, we can detect multiple analytes in the same sensing area simultaneously, besides that we can also effectively compensate for the errors caused by background index interference, and the refractive index change resulting from the non-specific binding, or physical absorption and others. It worth to say that by using this method, we can adjust and control the resonance wavelength by changing the fiber grinding angle, while keeping the testing sensitivity is not reduced. For practical applications, this reflective distributed fiber-based sensor is much suitable for biochemical sensing, it has small size and can enter a small testing spaces (μm scale). The diameter of the twin-core fiber is the only 125 μm, which helps to be integrated into a micro-fluidic chip. In this paper, we integrate the fiber probe into an infusion needle to simulate blood vessels on-line monitoring. [ABSTRACT FROM AUTHOR]

In this paper, the filtering properties of photonic crystals (PCs) to perform narrow-channel transmission-type filters in second and third optical fiber telecommunication windows have been studied. Filtration of these zero dispersion and low-loss windows have simultaneously been established by utilizing of a triple-cavity transmission-type one-dimensional PC that provides perfect transmittances and narrow-channels at corresponding wavelengths. Such PC-based optical filter can be used in wavelength division multiplexing (WDM) optical communications systems. [ABSTRACT FROM AUTHOR]

To increase the transmission capacity of optical fiber transmission systems, we have developed a multiplexer- digital-to-analogue converter and an optical time-division multiplexing modulator, which respectively generate high-speed signals in the electronic and optical domains. With these devices, we can significantly increase the capacity per wavelength channel. [ABSTRACT FROM AUTHOR]

High-order quadrature amplitude modulation (QAM) is a promising approach for increasing the spectral efficiency of wavelength-division-multiplexing transmission, but its optical implementation is still challenging. We propose a customized IQ modulator for generating 64-QAM using equal-amplitude electrical binary drive signals and verify the operation through simulations. Using the embedded VOAs, the transmitter can be finely controlled and flexible for several modulation formats. [ABSTRACT FROM AUTHOR]

We investigate the wavelength dependence of stress-induced time of flight variations in graded-index multimode fibers (GI-MMFs) for wavelength λ = 1.26 μm ∼1.58 μm, theoretically and experimentally. Calculations were made based on simple equations using the refractive index of silica fibers. We measured the wavelength dependence of stress-induced time of flight variations by a newly proposed measurement method. We confirmed the similar wavelength dependence of GI-MMFs to that for standard single mode fibers (SSMF). However, the value of them is different. We compare the experimental and theoretical results for two types of fibers. The comparison indicates that the difference of stress-induced time of flight variations between two types of fibers is mainly due to the group velocity difference. We conclude that there is no significant difference of the photo-elastic constant between the measured SSMFs and GI-MMFs. Although many properties of GI-MMFs depended on the mode power distribution in general, we conclude the dependence of stress-induced time of flight variations on mode power distribution is small for the measured fibers. [ABSTRACT FROM AUTHOR]

An optimal gain-flattened lumped Raman fiber amplifier (L-RFA), which was designed by cascading different chalcogenide fiber, was proposed and numerically demonstrated. The As-S fiber and the As-Se fiber were pumped by laser with different wavelengths. By solving the equation of the L-RFA, the characteristics including the gain and gain flatness of L-RFA are investigated. The results show that the L-RFA pumped by dual wavelengths can provide gain-flattened band from 1544 to 1558.4 nm with 0.0293 km fiber. Moreover, the average gain and gain flatness are 26.083 and 0.173 dB, respectively. The factors which influenced the output characteristics of L-RFA were also analyzed. [ABSTRACT FROM AUTHOR]

This paper presents a teletraffic study that evaluates the benefits of a passive optical access network, fix/mobile, by multiplexing wavelength division (WDM-PON) in which it is appreciated the impact of including extra wavelengths channels for the transmission of multicast services versus the multicast transport service using replicated unicast connections. The conclusion is that under heavy bulk-data traffic, the nominal data rate and tolerated efficiency are defined by the maximum number of out-of-profile users permitted for every multicast solution. Specifically, for the high values of efficiency the channels of extra wavelength avoid the need of multicast wavelengths used only when there is a fraction (significantly small) of out-of-profile users (5%). [ABSTRACT FROM AUTHOR]

A novel photonic crystal fiber (PCF) based on a four-hole unit is proposed in order to meet the requirements of high birefringence, negative dispersion and confinement loss in fiber-optic communication. The proposed design has been simulated based on the full vector finite element method (FVFEM) and anisotropic perfectly matched layers (APML). Analysis results show that the proposed PCF can achieve a high birefringence to the order of 10 −2 at the wavelength of 1.55 μm, a large negative dispersion over a wide wavelength range and confinement losses lower than 10 −9 dB/m simultaneously, which has important applications in polarization-maintaining (PM) fibers, single-polarization single-mode (SPSM) fibers, dispersion compensation fibers and so on. [ABSTRACT FROM AUTHOR]

We present a method for transmitting 25-Gb/s optical nonreturn-to-zero signals at a wavelength of 1550nm over a 40-km single-mode fiber without any dispersion compensation methods. We propose optimized self-phase modulation by varying parameters of the fiber launching power and the extinction ratio of optical non-return to zero signals to overcome severe signal distortions by the chromatic dispersion effect. Using the optimization of the self-phase modulation effect, we were able to transmit 25-Gb/s optical nonreturn-to-zero signals over a 40-km single-mode fiber, which can be applicable to passive optical networks with a single wavelength channel and a high split ratio. We demonstrated that the self-phase modulation effect can be controlled by the extinction ratio and the fiber launching power. [ABSTRACT FROM AUTHOR]

An ultra-wide wavelength tuning range, which covers three different band regions consisting of the S-, C-, and L-bands, is proposed and demonstrated for a graphene-based Q-switched erbium-doped fiber laser using a tunable bandpass filter as the wavelength tuning and filtering mechanism. A 3 m length of erbium-doped fiber is used as the gain medium in a ring laser cavity configuration, with absorption coefficients of between 11 and 13 dB m−1at 980 nm and about 18 dB m−1at 1550 nm. The tuning range of the Q-switching pulses covers a wide wavelength range of 58 nm, which spans from 1512.5 nm to 1570.5 nm. In addition, the lasing and Q-switching thresholds are considerably low, with respective values of ∼11.0 mW and ∼18.4 mW. A repetition rate of 55.3 kHz is obtained at the maximum pump power of 100.4 mW, together with pulse width and pulse energy of 1.6 μs and 25.8 nJ, respectively. [ABSTRACT FROM PUBLISHER]

Abstract: In this work, we investigate the performance of a distributed power control algorithm (DPCA) for signal-to-interference (SIR) optimization in wavelength-hopping time spreading code routed networks. These networks are based on 2D codes (time/wavelength) to establish end-to-end optical code paths (OCPs). The SIR model considers multiple access interference (MAI) between OCPs and amplified spontaneous emission (ASE) at cascaded amplified spans. The utilization of power control has a significant impact on both performance and capacity of practical optical networks. The DPCA can be effectively implemented in each node because uses only local parameters or measurements. [Copyright &y& Elsevier]

In this paper, we have experimentally demonstrated time domain characteristics of all-optical intensity modulation using cross-gain modulation induced by side-mode injection locking in a single-mode Fabry–Pérot laser diode (SMFP-LD). Both bistable hysteresis and injection locking behaviors are observed and discussed for different wavelength detuning between the injection beam and the selected side mode, which is the direct physical mechanism to successfully perform optical intensity modulation in the laser chip. Both the modulation depth of the injection signal and wavelength detuning have very important influences on the optical characteristics, including the modulation depth, and rise and fall time of the output signal at the dominant mode. The obtained modulation depth in the output signal can reach as high as ∼25 dB when a pulsed injection beam with a time duration of 8 ns is introduced into the laser chip under conditions of a bias current of 12 mA and an operating temperature of 16 ° C. [ABSTRACT FROM AUTHOR]

This paper presents an all-fiber tunable comb filter based on high-order mode fiber (HOMF). The filter is constructed by splicing a segment of HOMF between two sections of conventional single-mode fibers (SMFs), with an intentionally introduced offset at the first joint between the SMF and HOMF, and without an offset at the second joint between the HOMF and SMF, to optimize the visibility of the transmission spectrum. The optimal transverse offset of the fibers at the first joint and the tunable polarization-independent properties of the filter were studied theoretically and experimentally. An example of using this tunable comb filter in the application of a sensor, based on demodulating the wavelength shift of a fiber Bragg grating, has also been demonstrated. The particular advantages of this all-fiber tunable filter make it valuable in various applications. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate a random fiber laser operating at 1,115 nm using a LD-pumped Yb-doped fiber laser as the pump source. We achieve about 270 mW lasing output in a 50 km standard communication optical fiber with slope efficiency more than 28 %. A new wavelength is provided for the application of random distributed feedback fiber lasers as light sources. [ABSTRACT FROM AUTHOR]

In this article, we present the concept of the filterless optical network from a control plane perspective, defining the network and showing to what extent a control plane could be adapted to it. Then we propose a control plane architecture and study its performance. Filterless networks act as passive broadcast and select networks, in which active switching elements, such as the wavelength selection switch, are replaced by passive optical splitters and combiners, and network agility is provided by tunable transceivers. We introduce the concept of unfiltered channels and that of backward and forward ports, and show how they impact topological performance, and, in particular, the fact that wavelength usage increases greatly as the protection ratio shrinks. [ABSTRACT FROM PUBLISHER]

This paper presents a new passive optical network (PON) architecture that applies an optical multicast capable switch (OMS) to direct wavelengths to a set of PON branches and enables them to share the transceivers in the central office (CO) on demand. The OMS is composed of fiber splitters and switching gates, and by controlling the on-off gates the wavelengths at the inputs can reach any outputs of the OMS. Through the OMS configuration, logical PONs are dynamically formed according to changing traffic patterns, and traffic is further scheduled in the time domain within each logical PON. The proposed network achieves network resource sharing without requiring tunable transceivers or wavelength filters, and without changing deployed network devices in the field or at the user end. Analysis and experimental study results show the efficiency of resource sharing and demonstrate the concept of resource sharing among PON branches. [ABSTRACT FROM AUTHOR]

Abstract: A suppressant effect of wavelength competition for multi-wavelength lasing oscillations is experimentally demonstrated in an ordinary erbium-doped fiber laser (EDFL). The polarization hole burning is exploited by a segment of erbium-doped fiber (EDF) coiled round the plates of the three-loop polarization controller. The mechanism to suppress the wavelength competition is discussed in detail. Results show that the mechanism is helpful to obtain stable multi-wavelength lasing oscillations at room temperature in the EDFL. By properly adjusting the comb filter, three-wavelength and tunable dual-wavelength lasing oscillations have been achieved. The power fluctuation is measured to be less than 0.75dB over 30min for all the multi-wavelength lasing oscillations obtained in the experiment. The 3dB bandwidth of each lasing oscillation is 0.01nm and the 30dB bandwidth is 0.10nm. The side mode suppression ratio (SMSR) of the three-wavelength lasing oscillation is more than 45dB and that of the dual-wavelength lasing oscillations is more than 50dB. [Copyright &y& Elsevier]

Entangled states of light including low-loss optical fiber transmission and atomic resonance frequencies are essential resources for future quantum information networks. We present the experimental achievement on the three-color entanglement generation at 852, 1550, and 1440 nm wavelengths for optical continuous variables. The entanglement generation system consists of two cascaded nondegenerated optical parametric oscillators (NOPOs). The flexible selectivity of nonlinear crystals in the two NOPOs and the tunable property of NOPO provide large freedom for the frequency selection of three entangled optical beams. The presented system will hopefully be developed as a practical entangled source to be used in quantum-information networks with atomic storage units and long fiber transmission lines. [ABSTRACT FROM AUTHOR]

Abstract: Evolution of dual-wavelength fiber laser from continuous wave to soliton pulses is investigated experimentally by using the nonlinear polarization rotation technique. With the increase of pump power, the proposed laser successively delivers the dual-wavelength continuous wave, the single-wavelength soliton pulses, and the dual-wavelength soliton pulses. The dual-wavelength laser operates at the central wavelengths of about 1533 and 1546nm with the separation of ∼13nm. The number of soliton pulses operating in the dual-wavelength state is much larger than that of the single-wavelength state, while the pulse intensity always keeps constant. Experimental results reveal that the dual-wavelength mode locking is determined by the combination of pump strength and the cavity filtering effect. [Copyright &y& Elsevier]

Abstract: This paper presents a multi-functional all-optical device performs simultaneous chromatic dispersion (CD) monitoring, extinction ratio (ER) improvement and tunable wavelength conversion using four-wave mixing (FWM) in a single piece of highly nonlinear optical fiber (HNLF). The multi-functional ability arises from the nonlinear power transfer function (PTF) between the input signal and the output idler wave, which not only maps the CD information of the signal onto the average power of idler wave, but also transfers the data information to the idler wave with ER enhancement, making the device compact and cost effective. Furthermore within the wavelength tuning range the monitoring sensitivity and output ER can be much higher compared to all optical monitors and regenerators proposed before. Numerical simulations are then used to demonstrate the efficiency of this method. [Copyright &y& Elsevier]

Optical networking applications require the use of all-optical wavelength converters with input and output wavelength tenability as well as large numbers of multicasting channels. This article demonstrates the single-to-multiple wavelength conversion via multiple four-wave mixings between a 10-Gbit/s return-to-zero signal and several continuous waves co-propagating in a dispersion-flattened highly non-linear photonic crystal fiber. For single-to-single channel wavelength conversion, a wide conversion range of 31 nm is achieved with the optimal conversion efficiency of −21.4 dB. By employing several continuous-wave probe lights, tunable single-to-dual and single-to-triple channel wavelength conversions are experimentally demonstrated, respectively. Moreover, the dynamic characteristics of the designed wavelength converter are studied under the conditions of variable input powers, polarization mismatch, and different lengths of the highly non-linear-photonic crystal fiber. The system is transparent to both bit rate and modulation format. This is very useful for engineering design and applications of optical-fiber-based wavelength converters in future ultra-high-speed photonic networks. [ABSTRACT FROM AUTHOR]

In this paper, we propose the design of tunable and robust wavelength converters which can perform the polarity-preserved or polarity-inverted wavelength conversion by using the cross-phase modulation (XPM) in a dispersion-flattened highly nonlinear photonic crystal fiber (DF-HNL-PCF). The newly designed wavelength converter consists of a DF-HNL-PCF and an optical band-pass filter in the simple straight-line configuration, where XPM leads to broadening the spectrum of a continuous-wave probe light and the polarity-preserved, tunable wavelength conversion is then implemented by filtering out the blue-chirped or red-chirped spectral component of a probe light. The experimental results show that the polarity-preserved wavelength converter using a DF-HNL-PCF can achieve the error-free conversion of 10 Gbit s-1 optical data signals with the maximum power penalty of less than 2.1 dB over a wavelength range of nearly 34 nm. This wavelength tunability is actually limited by an operational wavelength range of the tunable optical band-pass filter that is used to extract the wavelength-converted signal in our experiment. Moreover, the polarity-inverted wavelength conversion is observed at the XPM-based wavelength converter using a DF-HNL-PCF, for the first time. This is achieved by tuning the central wavelength of an optical band-pass filter to coincide with that of a chirped probe light. [ABSTRACT FROM AUTHOR]

Abstract: A multichannel double-polarization bandpass optical filter, which has the performance of variable channel interval, is theoretically proposed. The filter consists of a stack of two one-dimensional photonic crystals (1D PCs). Based on the resonant couple of evanescent waves localized at the interfaces between neighboring layers, the linear transmission properties of the filter are numerically simulated by the transfer matrix method. The simulation results show that channel number of the filter can be changed by varying the thickness of the middle layer in the centrosymmetric 1D PC structure, while the bandwidth and wavelength of the channel can be adjusted by the incident angle of light. This work may be helpful in designing multichannel double-polarization bandpass optical filter in optical communication systems. [Copyright &y& Elsevier]

Abstract: Survivability is an important issue to ensure the service continuity in optical network. At the same time, with the granularity of traffic demands ranging from sub-wavelength-level to wavelength-level, traffic demands need to be aggregated and carried over the network in order to utilize resources effectively. Therefore, multi-granularity grooming is proposed to save the cost and reduce the number of switching ports in Optical-Cross Connects (OXCs). However, current works mostly addressed the survivable wavelength or waveband grooming. Therefore, in this paper, we propose three heuristic algorithms called Multi-granularity Dedicated Protection Grooming (MDPG), Multi-granularity Shared Protection Grooming (MSPG) and Multi-granularity Mixed Protection Grooming (MMPG), respectively. All of them are performed based on the Survivable Multi-granularity Integrated Auxiliary Graph (SMIAG) that includes one Wavelength Integrated Auxiliary Graph (WIAG) for wavelength protection and one waveBand Integrated Auxiliary Graph (BIAG) for waveband protection. Numerical results show that MMPG has the lowest average port-cost, the best resource utilization ratio and the lowest blocking probability among these three algorithms. Compared with MDPG, MSPG has lower average port-cost, better resource utilization ratio and lower blocking probability. [Copyright &y& Elsevier]

This article presents three new designs of photonic crystal fiber based intensity and wavelengths splitters/couplers. Numerical simulations have demonstrated the feasibility of planar and two-dimensional 1 × 8 intensity splitters/couplers using an optical signal having, respectively, a bandwidth of 1 THz and 125 GHz around a central wavelength of 1.55 μm. A wavelength demultiplexer has also been simulated for four wavelengths (each also having a bandwidth of 125 GHz) that belong to four telecom windows used in optical fiber communications. [ABSTRACT FROM PUBLISHER]

Abstract: A wavelength conversion based on high nonlinear microstructured fiber is demonstrated. Core diameter and pitch of the microstructured fiber used in this wavelength conversion method are 2.05μm and 5.0μm, respectively. Diameter of the air-holes in the fiber cladding is 4.50μm, the nonlinear coefficient of the microstructured fiber is 112.2W−1 km−1 and it is 60 times higher than that of a conventional dispersion-shift fiber, the length of the fiber is 100m. Four-wave-mixing effect is improved in the high nonlinear microstructure fiber and then the efficiency of the wavelength conversion is improved also. 10Gbps Not-Return-to-Zero (NRZ) modulation format and 10Gbps Return-to-Zero (RZ) modulation format are converted effectively by our method. This study can provide a new alternative solution for high effective all-light wavelength conversion in high speed optical communication systems with multi-wavelengths and all-light optical networks. [Copyright &y& Elsevier]

Abstract: A Dual-Wavelength Semiconductor Optical Amplifier (DW-SOA) based fiber ring laser with synchronous wavelength tunability is proposed and experimentally demonstrated. The SOA gain medium strongly suppresses mode competition, thus allowing stable dual-wavelength laser oscillation. The wavelength spacing of the two lasers can be tuned synchronously using a modified hybrid-tuning package incorporating a pair of Fiber Bragg Gratings (FBGs). The DW-SOA demonstrates a laser output with a wavelength spacing of between 0.10 and 8.30nm (wavelength shift inequality of 0.08 to 0.75nm). The relationship between the applied strain and wavelength shift of the two tuning modes is also analyzed. [Copyright &y& Elsevier]

A micro-displacement sensor consisting of a fiber-loop made with a tapered fiber is reported. The sensor operation is based on the interaction between the fundamental cladding mode propagating through the taper waist and higher order cladding modes excited when the taper is deformed to form a loop. As a result, a transmission spectrum with several notches is observed, where the notch wavelength resonances shift as a function of the loop diameter. The loop diameter is varied by the spatial displacement of one end of the fiber-loop attached to a linear translation stage. In a displacement range of 3.125 mm the maximum wavelength shift is 360.93 nm, with 0.116 nm/μm sensitivity. By using a 1,280 nm broadband low-power LED source and a single Ge-photodetector in a power transmission sensor setup, a sensitivity in the order of 2.7 nW/μm is obtained in ∼1 mm range. The proposed sensor is easy to implement and has a plenty of room to improve its performance. [ABSTRACT FROM AUTHOR]

Abstract: We demonstrate a tunable and switchable dual-wavelength passively mode-locked fiber ring laser in the anomalous dispersion regime that generates high-energy pulses at a sub-100kHz repetition rate. The nonlinear polarization rotation (NPR) technique is employed in this configuration to allow for passively mode-locked operation. By exploiting the intensity-dependent loss caused by NPR, the mode competition could be efficiently alleviated. Moreover, taking advantage of the intrinsic spectral filter induced by the intracavity birefringence, the dual-wavelength separations as well as the wavelength lasing locations could be flexibly tuned by properly rotating the polarization controller. With a repetition rate of 85.8kHz, the laser delivers the single pulse energy of 198nJ at a pump power of 250mW. The combination of high per-pulse energy and flexible tunability in this fiber laser is useful for practical applications. [Copyright &y& Elsevier]

Abstract: A sensor head consisting of a photonic crystal fiber (PCF)-based Mach–Zehnder interferometer (MZI) and a fiber Bragg grating (FBG) is proposed and experimentally demonstrated for simultaneous measurement of curvature and temperature. The MZI fabricated by splicing a short length of PCF between two single-mode fibers with the air-hole structure that completely collapsed near the splicing points, is sensitive to fiber bending and surrounding temperature, while the FBG is only sensitive to the later. Simultaneous measurement of curvature and temperature is therefore obtained. Sensitivities of 4.06nm/m−1 and 6.30pm/°C are achieved experimentally for curvature and temperature, respectively. And the corresponding resolutions are 5.2×10−4 m−1 and 1.25°C for curvature and temperature, respectively, based on the wavelength measurement resolution of 10pm. [Copyright &y& Elsevier]

Abstract: A microstructured polymer optical fiber (mPOF) with both ultra-flattened near-zero chromatic dispersion and high birefringence based on Topas cyclic olefin copolymer is designed. Three rings of uniform elliptical air holes are arranged in triangular lattice in the cladding and an extra small defected hole is introduced in the fiber core. Guided modes, dispersion, birefringence and mode confinement properties of the designed mPOF are investigated by using the full-vector finite element method. Dispersion values between ±0.5ps/km/nm over the wavelength 1.1–1.7μm and high birefringence of the order of 10−3 are obtained for the optimized fiber structure. Low confinement losses and small effective mode area are obtained at the same time. The relatively simple architecture of the proposed Topas mPOF can be fabricated by our extrusion-stretching techniques. [Copyright &y& Elsevier]

Abstract: We introduce a new measurement method of the nonlinear coefficient (NC) of a highly nonlinear fiber based on a four-wave mixing (FWM) technique. The NC along with the fiber''s zero-dispersion wavelength (ZDW) was determined from the precise measurement of the pump power dependent optimum pump frequency for peak FWM signal generation conditions. The measurement errors of the NC and ZDW values determined with this method were less than 4.6% and 0.051nm, respectively. [Copyright &y& Elsevier]