Superstructured Fiber Bragg Grating Research Articles

All-Optical 160-Gbit/s Retiming System Using Fiber Grating Based Pulse Shaping Technology

This paper demonstrates a retiming system operating at rates of 40 and 160 Gbit/s, which incorporates a superstructured fiber Bragg grating (SSFBG) as a pulse shaping element. The original data pulses are shaped into flat-topped (rectangular) pulses to avoid conversion of their timing jitter into pulse amplitude noise at the output of a nonlinear fiber-based Kerr switch. Thus retiming is performed in a single step avoiding wavelength conversion. The benefits of using shaped rather than conventional pulse forms in terms of timing jitter reduction are confirmed by bit-error rate (BER) measurements.

Field Trial of Duplex, 10 Gbps$\,\times\,$8-User DPSK-OCDMA System Using a Single 16$\,\times\,$16 Multi-Port Encoder/Decoder and 16-Level Phase-Shifted SSFBG Encoder/Decoders

An optical code-division multiple access (OCDMA) over wavelength-division multiplexing (WDM) system could be one promising solution to the symmetric gigabit access network with high spectral efficiency, cost effective, good flexibility and enhanced security. A cost-effective OCDMA/WDM system using a single multi-port en/decoder at an optical line terminal (OLT) and superstructured fiber Bragg grating (SSFBG) encoder/decoders at each optical network unit (ONU) in an optical network has been proposed and demonstrated. In this paper, we prepare 16-chip, 16-level phase-shifted SSFBG encoder/decoders and develop the full-asynchronous 10 Gigabit Ethernet (10 GbE) interface OCDMA prototype for the first time. Field trials of duplex, fully-asynchronous, 10 Gbps times 8-user DPSK-OCDMA system over 100 km using hybrid multi-port and SSFBG encoder/decoder are demonstrated.

基于超结构光纤光栅的双边带编/解码器

基于超结构光纤光栅的双边带编/解码器

A novel method of chirp elimination using reconstruction equivalent chirp superstructured fiber Bragg grating

A novel chirp elimination and pulse compression method is firstly proposed using reconstruction equivalent chirp superstructured fiber Bragg grating（REC-SSFBG）. Based on the feasibility of REC technology for any physical realizable target response， this novel chirp elimination method is suited for any model of chirped pulse. The simulation results show that the time bandwidth product decrease from 225， 265 and 250 to 0458， 0636 and 073 for linearly chirped， Gauss chirped and Lorentz chirped pulses， respectively. The original pulsewidth is 20 ps and the chirp coefficients is -5 for all the three cases. Further experiment is performed with a fabricated REC-SSFBG to compress a chirped pulse generated from commercial software with model of gain-switched distributed feedback laser diode. The pulsewidth decreases from 25 ps to 5 ps， which agrees well with the simulation.

相移超结构光纤布拉格光栅相位编/解码器的分析与设计

相移超结构光纤布拉格光栅相位编/解码器的分析与设计

Fibonacci quasi-periodic superstructure fiber Bragg gratings

Superstructure fiber Bragg gratings constructed following the Fibonacci sequence are proposed and simulated by using the transfer matrix method. The reflection spectrum has a multi-fractal structure as a function of the wavelength and is symmetric to the center. The reflectivity has self-similarity and scaling with respect to the Fibonacci sequence order at the central wavelength. For the transmission spectrum, the interaction of the core-cladding mode is investigated and the particular wavelengths for which the resonance condition is satisfied are located by varying the grating parameters. The potential application of the quasi-periodic structure as fiber sensors is also proposed.

Humidity fiber sensors based on superstructure fiber Bragg gratings coated with porous sol gel

AbstractA fiber sensor based on an etched superstructure fiber Bragg grating coated with the thin film of sol–gel is used for measuring the relative humidity. The operation mechanism of this sensor is based on that sol–gel materials can react with H2O molecules to result in its reflective index change and then to cause both Bragg wavelength shift. The diameter of the superstructure fiber Bragg grating is etched down to 20 μm for obtaining the sensitivity of 0.014 nm/1%RH. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 40–42, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23973

Design of superstructure fiber Bragg gratings with a Fourier analysis technique and its applications to multiple ultranarrow transmission gratings

Superstructure fiber Bragg gratings (FBGs) have been comprehensively analyzed with Fourier theory and experimentally demonstrated. By using Fourier transforms, it has been proven that (1) the traditional uniform FBG produces only a single response in the spectrum, (2) multiple phase-sampled gratings can be regarded as independent interleaved FBGs with different phases, and (3) the multiple phase sampling technique has the capacity to densify the spectral channels. Based on Fourier theory, for the first time to the author's knowledge, a kind of superstructure FBGs with multiple ultranarrow transmission windows, obtained by introducing a phase shift into the center of grating, is proposed and has been confirmed experimentally.

Code reusuable optical CDMA system using an array of superstructured fiber Bragg gratings

We have proposed a user extensible optical CDMA system which employs a repeated use of codes in the encoders and the decoders. In this study, we report the user-extension effect by using an array of superstructured fiber Bragg grating (SSFBG) as an encoder and a decoder through the simulations and the experiments. We performed the experiments by using 4 SSFBGs in each encoder and decoder. We have shown that the capable number of users can be increased up to 63C 1⋅ 63C 1⋅ 63P 2 when 63 orthogonal codes are used.

An Efficient Wavelength Converter Exploiting a Grating-Based Saw-Tooth Pulse Shaper

We experimentally demonstrate the generation of picosecond triangular optical pulses using a superstructured fiber Bragg grating and show experimentally that use of this pulse shape can provide a three-fold improvement in conversion efficiency relative to the use of Gaussian pulses with similar pulsewidths when used in a wavelength conversion scheme based on self-phase modulation and subsequent offset filtering.

Performance analysis of quadratic congruence codes using superstructured fiber Bragg gratings for a flexible data rate coherent DS-OCDMA system

The performance of a coherent direct sequence optical code division multiple access (DS-OCDMA) system using quadratic congruence codes implemented with superstructured fiber Bragg gratings is experimentally analyzed. We point out that nonperiodic and sparse quadratic congruence codes reduce multipath beat noise and intersymbol interference, respectively. These two properties of the structure of the quadratic congruence codes are shown to improve the bit-error-rate (BER) performance of the coherent system. As a result, we demonstrate that the performance enhancement of the coherent DS-OCDMA system allows the data bit rate of the system to be varied from 1 Gbit/sto2.5 Gbits/s and the receiver bandwidth to be decreased from 15 GHzto5 GHz respecting the low-cost requirement of the optical access network. These data bit rate and receiver bandwidth performances are achieved with moderate BER penalty.

Tunable Photonic Microwave Filter Using a Superstructured FBG With Two Reflection Bands Having Complementary Chirps

A tunable photonic microwave bandpass filter using a superstructured fiber Bragg grating (SFBG) with two reflection bands having complementary chirps is proposed. Being different from a regular chirped FBG, which is usually fabricated using a chirped phase mask with a fixed chirp rate, the SFBG with complementary chirps is fabricated using a uniform phase mask and a chirped sampling function. The chirp rate of the sampling function can be designed to realize specific equivalent chirp rates that are complementary in the 1st-order and the 1st-order reflection bands of the SFBG. An SFBG with complementary chirps is fabricated and characterized. The use of the SFBG to implement a photonic tunable microwave filter with a negative coefficient is experimentally demonstrated.

基于超结构光纤光栅的正交四相光码分多址编/解码器

基于超结构光纤光栅的正交四相光码分多址编/解码器

Performance Analysis of Phase-coding Based on Superstructured Fiber Bragg Grating

The performance of phase encoding and decoding based on phase shift superstructured fiber Bragg grating (SSFBG) in the optical code division multiplexing (OCDM) system was investigated and analyzed. The correlation characteristics for phase shift SSFBG based en/decoder were evaluated by considering input pulse width, grating refractive index modulation amplitude and wavelength mismatch between encoder grating and decoder grating. The impact of fiber dispersion on OCDM transmission over single-mode fiber (SMF) is also estimated. The theoretical results show that the degradation of coding performance is obvious under the impact of increasing of input pulse width, encoder-decoder wavelength mismatch and fiber dispersion, and there is a contradiction between correlation property and insertion loss of SSFBG en/decoder, we need to select moderate refractive index modulation amplitude of SSFBG grating.

A volatile-solvent gas fiber sensor based on polyaniline film coated on superstructure fiber Bragg gratings

A fiber sensor based on a polyaniline (PANI) film that is coated on the surface of an etched superstructure fiber grating to detect volatile solvent vapors is experimentally demonstrated. This sensing mechanism is based on the interaction of the testing gas with the polyaniline coating film, which changes the film index, resulting in a shift in the Bragg wavelength. The sensitivity of this sensor to ammonia (NH3) gas is about 0.073 pm ppm−1, which depends on the optical characteristics of the fiber grating, the diameter of the fiber cladding and the constituents of the sensing film. Methanol concentrations can also be measured using this sensing scheme. The sensitivity of this sensor must be improved to provide a simple, reliable, repeatable and non-destructive method for sensing various chemical gases.

Experimental demonstration of <inline-formula><math altimg="none" display="inline" overflow="scroll"><mrow><mn>40</mn><mspace width="0.3em" /><mi>Gbit</mi><mo>∕</mo><mi mathvariant="normal">s</mi></mrow></math></inline-formula> hybrid optical code-division multiplexing/wavelength-division multiplexing system

A 40 Gbit/s hybrid optical code-division multiplexing OCDM/ wavelength-division multiplexing WDM system is experimentally dem- onstrated and simultaneous multiwavelength optical encoding of a single supercontinuum source using superstructured fiber Bragg grating is achieved. The interchannel interference and noise of the OCDM/WDM system is suppressed apparently by incorporating a nonlinear amplifying loop mirror, both the sidelobe and the pedestal are reduced, the wave- form quality of decoded signal is improved, and the original 8.2 ps auto- correlation peak of decoded pulse is compressed to 4.8 ps. © 2007 Society

Impact of encoder-decoder wavelength mismatch on the performance of direct-sequence optical code-division multiple-access system

The impact on the performance of the direct-sequence optical code-division multiple-access (DS-OCDMA) system due to wavelength mismatch between encoder and decoder is investigated. Simulation results show that the encoder-decoder wavelength mismatch will degrade the bit-error-rate performance of the DS-OCDMA system drastically by decreasing the contrast ratio of the correctly and incorrectly decoded signals and lower data rate systems are more vulnerable to wavelength mismatch than higher data rate systems. In practical DS-OCDMA systems, the wavelength mismatch between encoder and decoder should be minimized, and some protective measures, such as temperature stabilization and fiber Bragg grating (FBG) packaging, should be taken to enhance the immunity of the superstructured FBG encoder/decoder to ambient conditions.

Ammonia gas fiber sensor based on poly‐aniline sensing film coated on superstructure fiber Bragg gratings

AbstractIn this study, we experimentally demonstrated that the concentrations of ammonia (NH3) gas can be detected by a fiber sensor based on the poly‐aniline (PANI) sensing film coated on the surface of an etched superstructure fiber Bragg grating (SFBG). This sensing mechanism is based on the NH3 gas to interact with the PANI‐coating film to cause the film index change and then to result in the Bragg wavelength shift. The sensitivity of this sensor is around 0.073 pm/ppm, which requires to be improved in the future for achieving a simple, reliable, repeatable, and nondestructive chemical‐gas fiber sensor. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 3063–3066, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22948

Experimental study on all optical coding and decoding of short pulses at 40‐Gbit/s

AbstractA 7‐chip, 280‐Gchip/s quaternary phase‐shift code is assigned to short pulses after reflection from an encoder, the code is then recognized by a decoder. The encoder and decoder, consisting of superstructured fiber Bragg gratings (SSFBGs), are fabricated using the equivalent‐phase‐shift method; only ordinary phase masks and submicrometer precision in control are required. The quaternary phase encoding and decoding of short pulses at 40‐Gbit/s is experimentally demonstrated, and it is required in optical code division multiplexing (OCDM) systems and packet‐switched networks. Interchannel interference noise is also considered and evaluated; a nonlinear optical loop mirror (NOLM) within the receiver is introduced to suppress the interference noise as well as additive noise. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2409–2412, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22747

Design of high reflectivity superstructured FBG for coherent OCDMA employing synthesis approach

For the first time to the authors' knowledge a design procedure of OCDMA en/decoders based on superstructured fibre Bragg gratings employing synthesis methods is proposed and experimentally demonstrated. Experimental results show a clear reduction of the insertion losses, maintaining unaltered the en/decoding capabilities in comparison with standard weaker devices.