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A dual-channel surface plasmon resonance (SPR) sensor, based upon a multimode-single mode-multimode-single mode- multimode (MSMSM) fiber structure, is reported for the simultaneous measurement of temperature and refractive index. One channel is coated with an indium tin oxide-silver layer for refractive index sensing, and the channel is coated with Au and cyclohexane layer for temperature sensing. The experiments show that the sensor provides high sensitivity with values of 3379 nm/RIU across the refractive index range from 1.333 to 1.3699 and −3.163 nm/°C from 40 °C to 90 °C. The cross-sensitivity problem is resolved by the dual-wavelength matrix method. Moreover, the proposed sensor has good stability, low cost, and a compact structure and may be employed in biology, chemistry, and environmental testing. [ABSTRACT FROM AUTHOR]

The advent of fiber optic technology in geophysics exploration has grown in its use in the exploration, production, and monitoring of subsurface environments, revolutionizing the way data are gathered and interpreted critically to speed up decision-making and reduce expense and time. Distributed Acoustic Sensing (DAS) has been increasingly utilized to build relationships in complex geophysics environments by utilizing continuous measurement along fiber optic cables with high spatial resolution and a frequency response of up to 10 KHz. DAS, as fiber optic technology examining backscattered light from a laser emitted inside the fiber and measuring strain changes, enables the performance of subsurface imaging in terms of real-time monitoring for Vertical Seismic Profiling (VSP), reservoir monitoring, and microseismic event detection. This review examines the most widely used fiber optic cables employed for DAS acquisition, namely Single-Mode Fiber (SMF) and Multi-Mode Fiber (MMF), with the different deployments and scopes of data used in geophysics exploration. Over the years, SMF has emerged as a preferred type of fiber optic cable utilized for DAS acquisition and, in most applications examined in this review, outperformed MMF. On the other side, MMF has proven to be preferable when used to measure distributed temperature. Finally, the fiber optic cable deployment technique and acquisition parameters constitute a pivotal preliminary step in DAS data preprocessing, offering a pathway to improve imaging resolution based on DAS measurement as a future scope of work.

In this paper, we design an ultra-dense wavelength division multiplexing (UD-WDM) system with 400 channels based on the differential phase-shift keying (DPSK) modulation technique and compared the performance of the proposed system with the one not having the DPSK modulation technique. The performance is investigated in terms of quality factor (Q-Factor) and bit error rate (BER) with varying transmission distance from 30 to 250 km and the number of channels from 50 to 400 for bit rates of 10 and 40 Gb/s per channel. The findings showed that the system with the DPSK modulation technique outperformed the system without the DPSK modulation technique for both 10 and 40 Gb/s bit rate per channel. The reported values of BER and Q-factor with transmission distance for DPSK modulated system for 10 Gb/s bit rate are around 10–9 and 14 dB respectively and for 40 Gb/s bit rate, the values are around 10–6 and 13.2 dB respectively, which are better than the values in the system without DPSK modulation technique which reported BER of around 10–3 and Q-factor of 4.2 dB for 10 Gb/s bit rate and BER of around 10–2 and Q-factor of 4.1 dB for 40 Gb/s bit rate. When the number of channels is taken into consideration instead of distance, the values of BER and the quality factor for DPSK modulated system is reported around 10–8 and 13.2 dB for 10 Gb/s bit rate and 10–6 and 9.2 dB for 40 Gb/s bit rate respectively which are better than the values in the system without DPSK modulation which reported BER of around 10–4 and Q-factor of 4.1 dB for 10 Gb/s bit rate and BER of around 10–1 and Q-factor of 4 dB for 40Gb/s bit rate. In the end, the eye diagrams for both the systems are compared and found better eye-opening in DPSK modulated system than the system without the DPSK modulation technique. [ABSTRACT FROM AUTHOR]

This paper presents a remote beamforming scheme with fixed wavelength allocation for radio-over-fiber (RoF) systems employing single-mode fiber (SMF). In the proposed scheme, wavelengths with equal narrow spacing are fixedly assigned to each antenna element to equalize the time delay differences between adjacent wavelengths caused by chromatic dispersion. The beam direction of base station (BS) is controlled only by phase control at central station (CS). This offers efficient wavelength utilization and completely remote beam control without information of optical fiber length, and supports systems employing high carrier frequency and long optical fiber. The beamforming performance of the scheme is evaluated theoretically and experimentally. It is shown that the beam pattern depends on optical intensity modulation frequency instead of radiated frequency. Simulations indicate that the required wavelength spacing to obtain a desired beam pattern becomes narrower as more wavelengths are used or intensity modulation frequency becomes higher. Finally, to evaluate the feasibility of the scheme, experiments are conducted under the condition of intensity modulation frequency of 10 GHz, 10 km SMF, and four element array antenna. The results substantially agree with the simulation results, and the main lobe level decrease is within 0.04 dB at wavelength spacing of 50–400 GHz (0.39–3.13 nm on average in C band). The results confirm that the scheme can achieve almost ideal beam patterns and realize beamforming and beamscanning. [ABSTRACT FROM AUTHOR]

The technology of long‐distance power supply with high‐power laser (HPL) over single‐mode fiber (SMF) is of great significance in specific environment. The nonlinear effect of fiber and photovoltaic conversion (PC) efficiency are the key factors restricting the application of this technology. The wide linewidth laser and cascaded long period fiber grating (CLPFG) band rejection filter are used to suppress the stimulated Brillouin scattering (SBS) and stimulated Raman scattering (SRS) effects, respectively, integrating sphere like, scattering light guide cone and thermoelectric power generation improve PC efficiency. A HPL over SMF remote power supply system is developed and tested. The injected fiber power is 10 W, the wavelength of 1550 nm laser is transmitted through 103 km single‐mode fiber, and then 26 mW power is converted for the sensor. This is also the highest level of the open literature. It is expected to be applied to the power supply of high voltage transmission line remote monitoring information system in remote areas. [ABSTRACT FROM AUTHOR]

Low-cost packaging and compact-size of optical fiber based optoelectronic devices and passive components have become vogue of enlargement in telecommunication, sensors and integrated circuits; therefore, it is an object of appreciable affair for packaging design to appraise the influence of misalignments during coupling. Efficient free-space coupling is predominant for achieving the communication systems with high bit rate at minimal loss values. Power coupling losses for lowest-order core-mode of large mode-area (LMA) hexagonal photonic crystal fibers (H-PCFs) in presence of misalignments (e.g., axial, radial and angular) with reference to input field is evaluated by utilizing the merits of an optical model. It is observed that LMA H-PCFs can be employed as appropriate aspirant for the efficient coupling strategy; moreover, theoretical results concerning coupling proficiency of classical SMF-28 are also studied. We investigated that LMA-10 PCF is not that sensitive to radial misalignment in contrast to the classical SMF; therefore, it can be utilized to frame manifold delays in optical true-time-delay (TTD) engines deployed on White cell concepts. The typical values of 1-dB tolerance are documented and the factors affecting coupling performance are also explored. Comparative results for the optimum butt-coupling loss are incorporated as articulated in the literature. [ABSTRACT FROM AUTHOR]

This paper evaluates the signal-to-cross talk ratio (SXR) of cross talk induced by stimulated Raman scattering (SRS) in radio-over-fiber (RoF) systems based on wavelength-division multiplexing. The reported study has modeled the relations of SXR to modulation frequency, optical power, transmission length, and effective area of fiber for various values of the walk-off parameter. The summary of experimental results reveals that SXR decreases with increases in channel input power and transmission distance and increased with increases in fiber effective area and modulation frequency. Results showed that increasing the walk-off parameter from 13.6 to 81.6 ps/km increased the SXR by almost 6 dBm. Furthermore, various fibers, including standard single-mode fiber (SMF), Corning LEAF, and Alcatel TeraLight were tested for their capacity to mitigate SRS-induced cross talk. These tests demonstrated that standard SMF suppressed SRS cross talk effectively and offered values of SXR 3 dBm and 6 dBm higher than the values exhibited by Alcatel TeraLight and Corning LEAF, respectively. [ABSTRACT FROM AUTHOR]

The simple structure of single-mode fibers as a sensing platform circumvents the technical bottlenecks associated with manufacturing difficulties. Meanwhile, compared to photonic crystal fibers, they have lower manufacturing costs and can achieve similar performance to other types of fibers, providing greater possibilities for mass production. The V-groove in the SMF destroys the original symmetry of the fiber and renders the core mode energy leak controllable, consequently enhancing the sensitivity and confinement loss (CL) intensity of the core mode as well as the resolution. The composite nanolayer (gold gas-sensitive film) combines the advantages of both the materials and mutual gain to strengthen the detection ability and continuously outputs high-quality free electrons to promote mode coupling. A dual-resonant-peak single-mode fiber (SMF) surface plasmon resonance (SPR) gas sensor with a V-groove is designed for the sensitive detection of methane and analyzed by the full-vector finite element method (FEM). By optimizing the structural parameters and polarization states, the SPR sensor can be operated in the concentration range between 0 % and 3.5 %, which can be spread across two transmission bands simultaneously with the maximum wavelength sensitivities being 12 nm/% and 8 nm/% and the corresponding resolution being 0.0083 % and 0.013 %, respectively. The tolerance of the structural parameters of the sensor is below 0.88 nm/μm to make manufacturing easier compared to conventional products. This sensor has good prospects and application potential in areas such as gas leakage diagnostics and environmental safety. [ABSTRACT FROM AUTHOR]

Microwave photonics is a prominent field in which photonic technologies are used to empower and extend the functionalities of microwave system which is a very tough exercise to fulfill directly in microwave domain. Focusing towards high power lasers to get a very short and intense pulse has forced to re-consider the possibilities of optical pulse compression at high energy. Pulse compression helps in generation of pulse of long duration and thus compress optical pulses to get the short pulse duration required for increasing the range-resolution of radar. A temporal pulse shaping approach for photonic generation of an arbitrary chirped microwave waveform with an increased time-bandwidth product (TBWP) is proposed and experimentally demonstrated in this paper. The main advantage of this proposed model is high time-bandwidth product (TBWP) in the range of 100-150 which leads to an increased range resolution of RADAR (Radio Detection and Ranging). [ABSTRACT FROM AUTHOR]

We propose the experimental transport of 48 channels with 40 Gbit/s dense wavelength-division multiplexing (DWDM) system that uses single-mode fiber (SMF) in combination with dispersion compensation fiber (DCF) which is a dispersion compensation device, in C and L band wavelength range to solve the dispersion program. The DWDM system scheme employing single Mach-Zehnder modulation (MZM) return-to-zero differential phase-shift keying (RZ-DPSK) modulation format with hybrid Raman/EDFA (Erbium-doped fiber amplifier) configuration to improve transmission signal, and employing an optical phase conjugation (OPC) configuration in the middle line. That can compensate for dispersion impairment and improve nonlinear effects to investigate transmission distance performances. [ABSTRACT FROM AUTHOR]

We design a spot-size converter (SSC) on silicon-on-insulator (SOI) platform to interface an integrated optical receiver (IOR) with a single-mode fiber (SMF). Because of the capability of coupling higher order modes by the proposed device, the tolerance of fiber-to-waveguide misalignment is much improved. The concept is suitable for receivers consisting of multimode-compatible components such as the echelle grating demultiplexer and the Ge waveguide photodetector.

The transmission performance of multichannel adaptively modulated optical orthogonal frequency-division multiplexing (AMOOFDM) signals is investigated numerically, for the first time, in optical-amplification-free and chromatic-dispersion-compensation-free intensity-modulation and direct-detection systems directly incorporating modulated distributed feedback (DFB) lasers (DMLs). It is shown that AMOOFDM not only significantly reduces the nonlinear wavelength-division multiplexing (WDM) impairments induced by the effects of cross-phase modulation and four-wave mixing but also effectively compensates for the DML-induced frequency chirp effect. In comparison with conventional modulated optical orthogonal frequency-division multiplexing (OFDM), which uses an identical signal modulation format across all the subcarriers, AMOOFDM improves the maximum achievable signal transmission capacity of a central WDM channel by a factor of 1.3 and 3.6 for 40- and 80-km standard single-mode fibers, respectively, with the corresponding dynamic input optical power ranges being extended by approximately 5 dB. In addition, AMOOFDM also causes the occurrence of cross-channel complementary modulation format mapping among various WDM channels, leading to considerably improved transmission capacities for all individual WDM channels.

In this work, numerical coupling efficiency calculations comparing single-mode fiber (SMF) to SMF coupling schemes using uncoated single ball, conic and graded-index (GRIN) rod lenses are discussed. The reported fiber coupling efficiency (FCE) calculations were performed using Huygens integral and Gaussian beam physical optics propagation (GBPOP) features in Zemax ® . The Huygens integral method results indicate that the FCE for ball, conic and GRIN rod single uncoated lenses (without accounting for Fresnel reflection and bulk absorption effects) can reach with the optimal lens and fiber parameters 91.11% (N-BK7 glass), 99.68% (N-BK7 glass) and 96.58%, respectively. In comparison, the calculated FCE for uncoated N-BK7 glass ball lens using the GBPOP method was 87.22% (without accounting for Fresnel reflections and bulk absorption effects). Furthermore, FCE calculations for ball lenses made out of sapphire, fused silica, S-LAH79 and N-LASF9 glass are given. The calculated deviation between the GBPOP and Huygens integral methods is <0.5%. Finally, tolerance analysis for each lens coupling scheme relating FCE to the tilts and the decentering of the lens and the two fibers is provided. The tolerance analysis calculations indicate that decentering of fibers and the single lens has the highest impact on the FCE values. Finally, FCE results suggest that the GRIN lens coupling scheme is the most sensitive scheme to misalignment and the ball lens scheme is the least sensitive to misalignment. [ABSTRACT FROM AUTHOR]

Temperature and vibration robustness of a reflecting all-fiber current sensor (AFCS) using a common single-mode fiber (SMF) are analyzed theoretically and experimentally. The effect of the birefringence condition of the sensing fiber on the temperature and vibration sensitivity of the AFCS is shown via theoretical models. The temperature and vibration sensitivity of the AFCS using an orthoconjugate retroreflector are almost entirely independent of the birefringence condition of the fiber. Thus, this configuration is preferable for a reflecting AFCS using an SMF. The experimentally observed temperature and vibration sensitivity of AFCSs using different fibers and configurations support this conclusion. [ABSTRACT FROM PUBLISHER]

The dependence of transmission characteristics on acoustic frequency for an SMF-based acousto-optic tunable filter has been investigated in this paper. Experimental results indicate that multi-resonance peaks may turn up in the transmission spectrum when applied acoustic frequency is sufficiently high, and resonance wavelengths increase in proportion to the applied acoustic frequency for short resonance wavelength region, while they have opposite acoustic frequency responses for longer resonance wavelength region. Our numerical simulation proves that this phenomenon could be attributed to the non-monotonic phase matching curves of acoustic gratings, which would be helpful for the understanding of mode coupling mechanism in fiber acoustic gratings and design of fiber-based acousto-optic devices. [ABSTRACT FROM AUTHOR]

Today, network systems require higher bandwidth for applications such as fiber-to-the-home communications. Gigabit passive optical network (GPON) links using a Fabry-Perot laser are attractive solutions for this high-speed network. However, due to the mode partition noise and fiber dispersion, GPON systems suffer from inter-symbol interference (ISI). In this paper, we present an electronic dispersion compensator (EDC) that will improve a 1.25-Gb/s experimental GPON link. The experimental GPON link is simulated and measured with impairment assessment. An analog eye-opening monitor, which captures the quality of the EDC output signal using the tunable delay and the integrator is proposed. The proposed EDC successfully compensates IS! for a given link with a 1.25-Gb/s signal. All circuits are fabricated using a 0.18-μm CMOS process. [ABSTRACT FROM AUTHOR]

A four-channel times10-Gb/s parallel optical transceiver for high-capacity very-short-reach applications was developed. The transceiver module was fabricated with low-cost components such as polymer planar lightwave circuit (PLC) platforms and 1.3-mum Fabry-Perot laser diodes (FPLDs). The polymer PLC platform enables the FPLDs or waveguide photodiodes (WGPDs) to be butt-coupled to the polymer waveguide by low-cost passive alignment. Using 1.3-mum FPLDs and single-mode fibers (SMFs) achieves reliable transmission over 600 m. Widening the spacing between the waveguides up to 1 mm suppressed the interchannel crosstalk to below -39 dB. The fabricated transceiver was operated at 10 Gb/s per channel and it successfully demonstrated 600-m error-free transmission. The sensitivity of each channel was better than -14 dBm with an interchannel-crosstalk penalty of less than 0.7 dB [ABSTRACT FROM PUBLISHER]

A novel bending single-mode fiber attenuator is presented. Organic glass plinths are sticked with several iron rods in order to impose bending on a typical single-mode fiber. Changing the space between the plinths, we can simultaneously determine bending magnitude and deduce the relationship between pure bend loss and bending-arc length. The theoretical model is in good agreement with the experimental results is stress-induced changes are considered. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 114–118, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21280 [ABSTRACT FROM AUTHOR]

A new method of coupling the light from a laser diode (LD) to a single-mode fiber with large alignment tolerances and without using any coupling lens is presented. A pseudovertical tapered coupler on silicon substrate which has an input aperture of about 100 times the size of the laser waveguide cross section is designed. Results showed that the coupler relaxes the LD placement tolerance and eliminates the use of a coupling lens. The positional tolerance between the LD and taper coupler can be larger than +/- 5 mu m in the xy plane, and +/-1 deg in orientation. [ABSTRACT FROM PUBLISHER]

External perturbation such as transverse force can increase the birefringence of most fiber Bragg gratings (FBGs). As a result, the interrogation accuracy of an FBG-based sensor may be significantly deteriorated due to an uncertain wavelength shift caused by the variation of polarization state of the input light. In the experiments, the reflection spectra of the FBG-based strain sensors made of the spun and conventional single-mode fibers were compared under different transverse forces when the polarized and unpolarized light was injected, respectively. It is shown that the spun FBG sensors have lower polarization dependence on, and consequently stronger resistance to, transverse force than the conventional FBG sensors [ABSTRACT FROM PUBLISHER]

• Optical model is utilized to explore optical performance of chalcogenide H-MOF. • An elegant approach based on linear combination of radii is adopted for evaluating n FSM. • Characteristics of slow-light enabled by SBS are investigated for As 2 Se 3 H-MOF. • Brillouin gain of ~87.6dB is achieved for 1m length of solid-core H-MOF at 1.06 µm. • Time-delay of ~137.1ns is obtained pumped with 100 mW of power in small-core H-MOF. The distinctive and prominent material characteristics of chalcogenide glasses, i.e., amorphous semiconductors containing one or more chalcogen elements have been examined due to their potential applications to enable the compact fiber lasers and amplifiers in mid-IR regime. Theoretical investigation based on an alternative optical model for the solid-core chalcogenide glass hexagonal lattice microstructured optical fiber (H-MOF) is explored for prompting the generation of slow-light facilitated through stimulated Brillouin scattering (SBS). Results are simulated for mode-area, nonlinearity coefficient, Brillouin gain, time-delay, and the admissible pump power levels. We noticed that from 1m length of single-mode chalcogenide H-MOF, Brillouin gain of about ~87.6dB and the time-delay of ~137.1ns is achieved at 1.06 µm pumped with 100 mW of power enabling the manifestation of slow-light in small core H-MOFs. For validation of the simulated results we included the comparisons with those as narrated in the literature. [ABSTRACT FROM AUTHOR]

All-optical subcarrier frequency conversion using an electrooptic phase modulator in a radio-over-fiber link is proposed and demonstrated. The frequency mixing is implemented by an electrooptic phase modulator, to which a local oscillator frequency is applied. The phase modulation to intensity modulation conversion is realized by using a length of single-mode fiber, which serves as a dispersive device. A subcarrier frequency conversion from 3 to 11.5 GHz performed over a 25-km radio-over-fiber link is experimentally demonstrated. [ABSTRACT FROM PUBLISHER]

A simple and efficient variable optical attenuator (VOA) is achieved by using microbend gratings on single-mode fiber (SMF). The flatness of the attenuator is maintained for 100 nm along the C+L band spectrum. Controlling the pressure will vary the attenuation depth of the device. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 463–465, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20668 [ABSTRACT FROM AUTHOR]