Demultiplexing using an arrayed-waveguide grating for frequency-interleaved DWDM millimeter-wave radio-on-fiber systems

The frequency-interleaved dense- wavelength-division-multiplexing (DWDM) millimeter-wave (mm-wave) radio-on-fiber is an indispensable technique to improve the optical spectrum efficiency. We propose possible configurations of multiplexing and demultiplexing (DEMUX) schemes using an arrayed-waveguide grating (AWG) with two input and N output waveguides (N: total channel number). In this paper, we focus on the DEMUX scheme and experimentally demonstrate the DEMUX scheme using a commercially available AWG. In the experiment, 25-GHz-separated two-channel optical double sideband signals modulated by a 60-GHz millimeter-wave carrying a 156-Mb/s data are optically multiplexed by the frequency interleaving. The power penalty after DEMUX, which was due to interchannel interference, was less than 0.5 dB. We also made a transmission experiment over 25-km standard single-mode fiber (SMF). No noticeable power penalty in the received data due to chromatic dispersion of the transmission fiber was observed. This is because only the carrier and a sideband are detected in the proposed DEMUX scheme.     

Low-crosstalk 10-GHz-spaced 512-channel arrayed-waveguide gratingmulti/demultiplexer fabricated on a 4-in wafer

We report a 10-GHz-spaced 512-channel arrayed-waveguide grating (AWG) multi/demultiplexer fabricated on a 4-in wafer. We achieved this by folding the 7-cm-long slab waveguides of a conventionally configured AWG, so that the whole configuration was contained in the wafer and then attached reflecting mirrors at the folded parts. Phase compensation of the fabricated AWG was performed by means of ultraviolet irradiation through a metal mask     

Filling the frequency gaps of a planar optical spectrum analyzer using a 2.5-GHz-spaced arrayed-waveguide grating in the C and L bands

A vernier configuration in a 2.5-GHz-spaced 128-channel arrayed-waveguide grating (AWG) for use as a secondary demultiplexer in a planar optical spectrum analyzer was incorporated with a tandem configuration. The frequency changes were 3.0 and 2.5 GHz for adjacent input and output ports, respectively. By selecting any of the eight input ports of the AWG, new passbands could be generated in the gaps between adjacent passbands and in the gaps produced when the diffraction order of the AWG was changed. Enough new passbands were generated to achieve frequency sampling at 1-GHz intervals without dead frequency points in the C and L bands of optical fiber amplifiers.     

A 16-channel frequency selection switch for optical FDMdistribution systems

The performance of a 5-GHz-spaced, 16-channel frequency selection switch (FS-SW) for optical frequency division multiplexing (FDM) distribution systems is described. The silica waveguide-type FS-SW is constructed with four serially connected periodic filters integrated on a silicon chip. The required crosstalk level for each periodic filter of the FS-SW was estimated to be -21.0 dB for a 16-channel FS-SW and 23.6 dB for a 128-channel FS-SW. Crosstalk can be independent of the power coupling ratio of the 3-dB-coupler regions by choosing suitable connecting configurations for the periodic filters. A controller for the switch is also described and the desired channel can be selected successfully from among 16 optical carriers under an average crosstalk level of less than -20 dB     

Performance of erbium-doped fibre amplifier in 16-channel coherent broadcast network

The performance of an erbium-doped fibre amplifier in a 16-channel coherent broadcast network operating at 155 Mbit/s has been experimentally investigated. A fibre-to-fibre gain of 22 dB at 1540 nm allowed simulation of a network that serves 256 end-users over a distance of 102 km.<>     

10 Gbit/s based NRZ DWDM systems using polarisation switching in single wavelength channel

It is experimentally demonstrated that the nonlinear tolerance of 10 Gbit/s/ch NRZ based DWDM systems over 1500 km standard singlemode fibre can be significantly improved through the use of orthogonal polarisation switching between adjacent bits in a single wavelength channel.     

Measurement of slowly varying component in phase error distribution of a large-channel-spacing arrayed-waveguide grating

It has been difficult to measure the phase error distribution of a large-channel-spacing arrayed-waveguide grating (AWG) with optical low coherence interferometry (OLCI). In this reported work OLCI was successfully used to measure the slowly varying component in the distribution of a 1 THz-spaced AWG that was the primary filter in an ultra-high-density multi/demultiplexer. The spectral sidelobe of the AWG can be reduced by using the component to achieve the lowest possible accumulated crosstalk in the multi/demultiplexer.     

A.2.5 GHz-spaced 1080-channel tandem multi/demultiplexer coveringthe. S-, C-, and L-bands using an arrayed-waveguide grating withGaussian passbands as a primary filter

We describe a low-loss 25-GHz-spaced multi/demultiplexer with more than 1000 channels that covers the S-, C-, and L-bands of optical fiber amplifiers. It was achieved by cascading a 2.5-THz-spaced arrayed-waveguide grating (AWG) with Gaussian passbands as a primary filter and ten 25-GHz-spaced 1×200 AWGs as secondary filters in a tandem configuration     

DWDM系统光纤光栅分插复用器的设计与实现

综合分析了均匀光纤光栅主反射带内、外反射谱和透射色散特性对DWDM系统光波分插复用的影响，分析计算了DWDM系统中信道参数与光纤光栅参数之间的关系，在此基础上，对用于波分复用系统信道间距分别为50/100GHZ的光波分插复用的光纤光栅进行了设计，并在实验中刻制出相庆的光纤光栅。     

Machine learning-based regression models for predicting signal quality of dense wavelength division multiplexing (DWDM) optical communication network

Over the years, optical communication systems have been a significant source of fast and secure communication. However, factors like noise and mitigation error can degrade the bit error rate (BER) and quality factor (Q factor) of optical communication systems. Predicting the optimal threshold, Q factor, and BER is usually a difficult task. Therefore, in this paper, machine learning-based linear regression, least absolute shrinkage and selection operator (LASSO) regression, and Ridge regression have been used for a dense wavelength division multiplexing (DWDM)-based optical communication network to predict the signal quality. These techniques have been used to predict the desired BER, Q factor, threshold, and eye height of the system. To demonstrate this research concept, a DWDM-based optical communication network of 50 km length is designed and simulated using Optisystem-14.0. After data preparation, regression models have been developed and validated through diagnostic plots. Results show that mean square error (MSE) has a significant decline with an increase in the number of epochs for all four models. LASSO and Ridge regression have effectively resolved the issue of overfitting, which occurred in the linear regression case. Furthermore, the mean MSE plot proved the significant reduction of mean MSE in the case of LASSO regression. Results show that min BER for LASSO regression came out to be −173,627.14, providing a robust and cost-efficient process.     

MEMS tunable SOI waveguide Bragg grating filter with 1.3 THz tuning range for C-band 100 GHz DWDM optical network

A MEMS tunable integrated waveguide Bragg grating-based filter for C-band optical dense wavelength-division multiplexing (DWDM) network is presented and analyzed in this work. Waveguide Bragg grating being a notch filter in the transmission spectrum is used to realize a tunable filter by varying the applied voltages to the fixed–fixed beam loaded with this grating. The strain across the grating is enhanced by choosing MEMS beam configuration such that the metal electrode is the bottom-most layer of the composite fixed–fixed beam. Device dimensions are chosen to achieve a narrow full width half maximum of 0.77 nm, allowing filtering of adjacent channels of 100 GHz DWDM network. A large Bragg wavelength shift of 10.4 nm (1552.52–1562.92 nm) was achieved at 45.8 V actuation providing tuning for 14 DWDM channels with inter-channel cross talk below ? 21 dB, with tuning range of 1.3 THz.

     

Application of the saddle point method for the evaluation of crosstalk implications in an arrayed-waveguide grating interconnection

The effect of in-band crosstalk can pose severe limitations in an optical network. In this paper, the implications of in-band crosstalk induced by an arrayed-waveguide grating (AWG) router in a passive N/spl times/N optical interconnection are analyzed with non-Gaussian statistics using a numerical model. The model is based on the saddle point approximation and takes into account fluctuations of the transfer function's sidelobes induced by the phase errors in the grating arms, phase noise, polarization variations, bit misalignment, and shot and thermal noise. The influence of these effects on the interconnection's bit error rate (BER) is analyzed. The validity of the Gaussian assumption for the crosstalk noise statistics is discussed. Finally, the model is used to examine the mean crosstalk requirements for various numbers of network nodes.     

Demonstration of a 1*2 multichannel grating cavity laser for wavelength division multiplexing (WDM) application

A new form of diode laser source for wavelength-division multiplexing (WDM) applications is reported. The source has been designed to operate in systems requiring wavelength separations between channels of more than 1 nm and provides exact control of channel separation with low crosstalk. Simultaneous multiwavelength generation is also possible.<>     

频谱分割DWDM无源光网络系统串扰实验研究

设计实现了基于宽光源频谱分割密集波分复用无源光网络(DWDM-PON)的实验系统。针对于相邻信道和非相邻信道串扰,通过串扰理论模型分析、系统实验测试得出的丢包率和光谱图比较了二者的影响;对比了理论和实验中DWDM-PON系统的串扰功率代价。结果表明:在信道间隔为0.8nm、速率为125Mbit/s的情况下,相邻信道串扰带来的光功率代价约为0.2dB;相邻信道引起的串扰远大于非相邻信道引起的串扰,非相邻信道引起的串扰影响可以忽略。     

Phototransistors in digital optical communications systems for 1?1.6 ?m wavelength

Receiver sensitivity comparable with that of a PIN-FET hybrid should be attainable using phototransistors at bit rates below 1 Gbit/s. However, significant improvement would call for a phototransistor having a very low input capacitance C and a high current gain hFE satisfying C<2×10?3?(hFE) pF, incorporated into an integrating receiver design.     

Monolithic integrated wavelength demultiplexer based on a waveguideRowland circle grating in InGaAsP/lnP

We present detailed modeling and experimental results for an improved design of an InGaAsP-InP wavelength demultiplexer based on a monolithically integrated Rowland circle grating. The design incorporated ten wavelength channels at 1.55 μm with a uniform spacing of 2 nm. The total on-chip loss was about 10 dB and the crosstalk between adjacent channels was as low as -25 dB. It was shown that low-loss etched turning mirrors can reduce the total on-chip loss by about 4 dB compared to traditional 90° curved multimode waveguides. By replacing standard flat grating facets with retro-reflecting V-shaped facets in the echelle grating, the loss was further reduced by 4 dB. Polarization independent operation within a passband of 0.5 nm was achieved by using multimode output waveguides. The potential sources producing the crosstalk have been analyzed and fabrication modifications for further improvement are suggested     

A synthetic algorithm for wavelength routing in optical network

After analyzing the merits and shortcomings of Fixed-Alternated Routing algorithm （FAR） and Least Loaded Routing algorithm （LLR）, we propose one novel dynamic optical routing algorithm. Having considered the influences of path＇s length and path＇s congestion just like in FAR and LLR, we take into account the network resource status-amount of free wavelengths in the network. Proposed algorithm sets up connections on three possible paths according to amount of available free wavelengths in the network, which effectively decreases the blocking probability. The National Science Foundation （NSF） network and mesh-torus network simulation results show that the performance of this algorithm is better than that of FAR and LLR.     

Channel selection and stabilization technique for a waveguide-type16-channel frequency selection switch for optical FDM distributionsystems

A channel selection and stabilization technique for a waveguide-type 16-channel frequency selection switch (FS-SW) was examined at the 1.5-μm wavelength region. The desired channel could be selected from 16 optical channels with a 5-GHz channel separation. The frequency fluctuation width for the observed short period was 65-250 MHz, and the frequency drift during 30 min was 20-100 MHz. An average crosstalk level of less than -20 dB was successfully achieved in the on state of the FS-SW stabilization