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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]

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]

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]

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]

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]

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]

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]

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]

Abstract: A novel polarizer is designed by liquid filling in partial air-holes of a hollow-core photonic bandgap fiber (PBGF) forming an asymmetric waveguide structure, which leads to the vertical polarization light leaking out while the horizontal polarization light remaining to propagate along the fiber with a relatively low loss. Applied with a full-vector finite-element (FEM) method, a series of polarizer structures with different water-filled regions has been simulated for a better performance on the polarization extinction ratio and the insertion loss. Through optimization, the proposed PBGF polarizer has a high polarization extinction ratio of more than 32dB in the operation wavelength range from 1530nm to 1600nm. [Copyright &y& Elsevier]

Abstract: We demonstrate a Dynamic Capacity Allocation scheme for the realization of Moving Extended Cells in Radio-over-Fiber networks. Our scheme exploits a reconfigurable MEMS-based Central Office architecture for routing of and switching between six data carrying wavelengths, forming in this way cell clusters that transmit the same information content and can move with the mobile user. Error free transmission through 25km SMF is presented for a 5-cell MEC structure, with each optical channel carrying 500Mb/s data subcarrier-modulated at 8.5GHz. [Copyright &y& Elsevier]

Abstract: We investigate the dispersion property of space filling mode of photonic crystal structures and find a new type of dispersion—structure induced dispersion. By incorporating this new source of dispersion we designed PCF with large normal dispersion ~350ps2/km. Our simulation indicates the dispersion of such fiber changes less than 3% in 1.4–1.7μm wavelength range and we also show that our design is insensitive to the structure changes. [Copyright &y& Elsevier]

Abstract: A tunable and switchable single-longitudinal-mode (SLM) dual-wavelength fiber laser incorporating a reconfigurable dual-pass Mach–Zehnder interferometer (MZI) filter was proposed and demonstrated, which can be applied in microwave generation. By incorporating a high extinction ratio (ER) dual-pass MZI into an erbium-doped fiber ring cavity, SLM dual-wavelength lasing can be achieved even using a MZI with relatively little free spectrum range (FSR), and by beating the two wavelengths at a photodetector, a 9.76GHz microwave signal with a 3-dB bandwidth of less than 10kHz is obtained. Moreover, by direct linking the two outputs of the MZI, the high ER dual-pass MZI is easily reconfigured as a half FSR dual-pass MZI. Using this structure, switchable SLM dual-wavelength lasing can be conveniently realized. [Copyright &y& Elsevier]

Abstract: A triple sampling method to have enabled excellent channel uniformity and high in-band energy efficiency is firstly proposed for the design of an ultrahigh-channel-count fiber Bragg grating (FBG), which is based on the simultaneous utilization of two amplitude-assisted phase sampling (AAPS) functions and a phase-only sampling (POS) function. As an example, one linearly chirped FBG with consecutive 1215 channels enabling to cover all fiber telecom bands (O+E+S+C+L+U) is numerically demonstrated, which has a length of 9cm, a dispersion of −1360ps/nm, and a channel spacing of 50GHz. The maximum index-change required for 10dB strength of the FBG is less than 6×10−3. [Copyright &y& Elsevier]

Abstract: In this paper we report on the characterization of a narrow linewidth three-section tunable slotted Fabry–Perot laser. The SMSR of the 25 available 100-GHz ITU channels is above 30dB, whereas their average linewidth is 538kHz with a maximum below 800kHz. The RIN spectra of six different channels are also measured and a maximum average RIN of −135dB/Hz is obtained. The linewidth effect of the laser in a 1.25Gb/s DPSK transmission system is investigated by comparing the performance between the slotted Fabry–Perot laser and a commercial SG-DBR laser respectively. Error free transmission of the slotted Fabry-Perot laser shows the benefit of the narrow linewidth of the device for systems employing advanced modulation formats. [Copyright &y& Elsevier]

Abstract: In order to save the switching ports and the cost of Multi-Granularity Optical Cross-Connect (MG-OXC), the waveband switching technique was proposed to groom multiple wavelength-level traffic to a few waveband tunnels to be switched by a few switching ports in MG-OXC. At the same time, protection for fibers is very important to ensure the service continuity since each wavelength carries a lot of traffic. Although existing works have addressed the waveband switching protection, most of them separately considered only the dedicated protection or shared protection in static demand scenario and did not deeply analyze and compare the dedicated protection and shared protection in dynamic demand scenario. Therefore, in this paper, we deeply study the consumptions of wavelengths in fibers and ports in MG-OXCs for Waveband Shared Protection (WSP) and Waveband Dedicated Protection (WDP) in dynamic demand scenario, and propose the port-cost calculation and update methods based on a new waveband layered auxiliary graph that is developed based on MG-OXC structure. In simulations, we compare WSP, WDP, traditional end-to-end waveband shared protection and traditional end-to-end waveband dedicated protection. Simulation results show that the shared protection has smaller port-cost, better wavelength utilization efficiency and lower blocking probability than the dedicated protection with the same waveband switching policy, and the sub-path waveband switching has bigger port-cost, better wavelength utilization efficiency and lower blocking probability than the end-to-end waveband switching with the same backup wavelength assignment policy. [ABSTRACT FROM AUTHOR]

Abstract: Simultaneous wavelength conversion of multichannel polarization shift keying (PolSK) signal using four-wave-mixing in highly non-linear fiber is demonstrated. In the proposed wavelength converter, the wavelengths of four 10-Gb/s polarization shift keying channels are simultaneously converted without any performance degradation for the converted channels. We successfully achieved high conversion performances for all the converted channels even though the input PolSK channels have different delay time and state of polarization. [ABSTRACT FROM AUTHOR]

Abstract: The comprehensive characters of delay time and delay bandwidth with distortion, signal wavelength dependence and delay bandwidth product in fiber optical parametric amplifier are investigated theoretically when the pump locates at anomalous dispersion region. The delay character of single pulse, data stream with certain bit pattern and pseudo random data stream are analyzed comprehensively. In this category of fiber optical parametric amplifier, the delay time and delay bandwidth product vary from signal wavelengths and bit rates. For the same nonlinear coefficient, pump power and fiber length, the diverse dependences of bit pattern in different signal wavelengths are found by numerical simulation. The impacts of pump power and fiber length on the delay character and distortion are also discussed. These relations are conductive to the design of slow light based on fiber optical parametric amplifier in telecommunication waveband. [ABSTRACT FROM AUTHOR]

Abstract: A multiwavelength actively mode-locked fiber ring laser that utilises a single semiconductor optical amplifier as both a gain and mode-locking element is presented. It is verified experimentally that the number of mode-locked wavelengths may be maximised by compensating for the anomalous intra-cavity dispersion. This is achieved through the inclusion of an appropriate length of normal dispersion fiber in the laser cavity. Using this technique, the number of wavelengths simultaneously mode-locked at 10GHz was increased from 2 to 5. [Copyright &y& Elsevier]

Abstract: I present new method of phase modulation to amplitude modulation conversion (PM/AM conversion) that utilizes integrating capabilities of fiber Bragg grating (FBG). I found that the wavelength converter based on fiber cross-phase modulation (XPM) and new method of PM/AM conversion have an order of magnitude higher conversion efficiency then the wavelength converter based on sideband filtration method and up to 6dB higher conversion efficiency then the converter based on the nonlinear optical loop mirror. Numerical analysis and experimental results are provided for bit rates up to 40Gb/s. [Copyright &y& Elsevier]

Abstract: An experimental study of stability between two types of short-cavity laser configurations is carried out. The short-cavity lasers are comprised of one or two pairs of wavelength-matched FBGs, encompassing a short length of highly-doped Er-fiber, to create effectively single- or dual-wavelength fiber lasers. The laser performance in terms of the laser output power and laser stability in relation to the gain medium length was investigated experimentally, analyzed and reported in this letter. [Copyright &y& Elsevier]

Abstract: We have investigated the effects of cladding etching in arc-induced long-period fiber gratings. Comparing the position of the resonant wavelengths at each diameter with the corresponding theoretical dispersion curves of effective refractive index, it is found that some of the resonances show a better match with anti-symmetrical cladding modes, while others with symmetrical cladding modes. Etching the cladding diameter to ∼39μm, results in coupling to a high-order cladding mode that is very sensitive to changes in the ambient refractive index. The resonant peak shifts remarkably (∼230nm) toward shorter wavelengths as the external refractive index increases. This sensitivity is higher than any previously reported in arc-induced long-period fiber gratings. [Copyright &y& Elsevier]

Abstract: We demonstrate a multiwavelength fiber laser with ultradense wavelength spacing and ultrabroad bandwidth based on inhomogeneous loss mechanism with assistance of nonlinear polarization rotation. The inhomogeneous loss, implemented by incorporating a section of highly nonlinear fiber (HNLF) and a Sagnac filter in the laser cavity, can balance mode competition in erbium-doped fiber and result in ultradense multiwavelength generation. The bandwidth of the multiwavelength spectrum is greatly broadened owing to the intensity-dependent loss induced by nonlinear polarization rotation. Stable multiwavelength lasing with wavelength spacing of 0.08nm and wavelength number up to 254 is achieved at room temperature. Moreover, multiwavelength tuning is realized through modifying polarization-dependent cavity loss. [Copyright &y& Elsevier]

Abstract: We report a novel single linearly polarized, widely, freely and continuously tunable two wavelengths -doped fiber laser. The laser generates stable arbitrary two wavelengths output between 1003.1 and 1080.7nm peak wavelengths simultaneously with a 346.0mW CW power by using polarization beam splitting (PBS) for separation of two wavelengths. Each lasing line shows a single polarization with a polarization extinction ratio of >20dB under different pump levels. The central and the interval of the two wavelengths can be tuned smoothly and independently in the entire gain region of >70nm of PM -doped single mode fiber. Strongly enhanced polarization-hole burning (PHB) phenomena in polarization maintain (PM) -doped fiber was observed in the tunable two wavelengths -doped fiber laser. [Copyright &y& Elsevier]

Abstract: We report design and subsequent fabrication of an intrinsically gain flattened Erbium doped fiber amplifier (EDFA) based on a highly asymmetrical and concentric dual-core fiber, inner core of which was only partially doped. Phase-resonant optical coupling between the two cores was so tailored through optimization of its refractive index profile parameters that the longer wavelengths within the C-band experience relatively higher amplification compared to the shorter wavelengths thereby reducing the difference in the well-known tilt in the gains between the shorter and longer wavelength regions. The fabricated EDFA exhibited a median gain ⩾28dB (gain excursion below ±2.2dB within the C-band) when 16 simultaneous standard signal channels were launched by keeping the I/P level for each at −20dBm/channel. Such EDFAs should be attractive for deployment in metro networks, where economics is a premium, because it would cut down the cost on gain flattening filter head. [Copyright &y& Elsevier]

Abstract: We have experimentally and theoretically demonstrated the transmission performance of a feedforward optical transmitter using an external light injection technique. The feedforward compensation method shows 31dB intermodulation distortion suppression and 2.2dB noise reduction. The feedforward architecture used a wavelength-locked Fabry–Perot laser diode whose side-mode suppression ratio about 35dB over a 12-nm range. The suppression characteristics of the intermodulation distortion for various wavelength differences and transmission lengths were measured and analyzed as the evaluation criteria for the system performance in WDM/SCM based radio-over-fiber systems. [Copyright &y& Elsevier]

Abstract: A novel wavelength-selective all-fiber filter using a single long-period fiber grating (LPG) interacting with a misaligned fusion splicing point has been demonstrated. The misaligned splicing point couples a part of the core mode power into the cladding modes, which is then recoupled into the core mode by the following LPG. As an optical path difference is introduced by the differential refractive index of the fiber, an in-fiber Mach–Zehnder interferometer is therefore formed, which may function as a cost-efficient WDM filter with good isolation and low insertion loss. [Copyright &y& Elsevier]