Influence of Crosstalk on Signal Power Based on Arrayed-waveguide Grating as N × N Optical Router

The fact that the signal results in signal-crosstalk is confirmed for arrayed-waveguide grating as N × N optical router,and the relation between the crosstalk and power penalty is obtained.The method reveals the random distributions of optical path phase errors in two multiplexers with channel numbers of 10 and 160. It is shown that the crosstalk must be less than -28 dB for a power penalty below 1 dB at a bit error rate of 1×10 -9 .It is found that when N =100,crosstalk power value is -20 dB with compensation power of 2-3 dB,so the compensation power is not ignored.     

FDM-channel selection filter employing an arrayed-waveguide gratingmultiplexer

A novel channel selection filter based on an arrayed-waveguide grating multiplexer is reported for optical frequency-division-multiplexer (FDM) networks. The filter employs fold-back optical paths and optical switches, and can be operated digitally with multiple switches. A 16 channel selection filter employing a silica-based 16×16 multiplexer achieves a 20 GHz bandwidth and a crosstalk of less than 27 dB     

Multichannel frequency-selective switch employing anarrayed-waveguide grating multiplexer with fold-back optical paths

The optimized configuration of an N-channel frequency-selective 2×2 switch based on an arrayed-waveguide grating (AWG) (2N+1)×(2N+1) multiplexer is proposed that offers significant crosstalk reduction and loss-imbalance equalization. The optimization is achieved by employing fold-back optical paths instead of loop-back paths. A switch constructed with a silica-based AWG 16×16 multiplexer demonstrates coherent crosstalk of less than -30 dB in the transmitting frequency-division-multiplexed (FDM) channels; the gain in optimization is more than 15 dB. The largest loss-difference among the seven FDM channels is simultaneously reduced from 4.5 dB to 1.6 dB. These improvements will extend the cascadable number of nodes in all-optical FDM networks     

Flat spectral response arrayed-waveguide grating multiplexer withparabolic waveguide horns

An eight-channel flat spectral response arrayed-waveguide grating multiplexer with parabolic waveguide horns has been fabricated on a planar lightwave circuit (PLC). A double-peaked intensity distribution is formed at the slab interface by the parabolic waveguide horn. A 1 dB bandwidth of 98 GHz, 3 dB bandwidth of 124 GHz and 20 dB bandwidth of 196 GHz are obtained for 200 GHz channel spacing. The crosstalk to neighbouring channels is less than -27 dB and the on-chip insertion losses range from 6.1 to 6.4 dB, respectively     

Impact of crosstalk in an arrayed-waveguide multiplexer onN×N optical interconnection

The impact of crosstalk in an arrayed-waveguide N×N wavelength multiplexer is investigated precisely in relation to its application to wavelength-routing N×N all optical networks. In such systems multiple crosstalk light which has the same wavelength as the signal results in signal-crosstalk beat noise. We confirm that the noise is Gaussian and obtain the relation between crosstalk and power penalty. It is shown that the crosstalk must be less than -38 dB for a 16×16 system to keep the power penalty below 1 dB at a bit error rate of 10^-9     

Polarization-independent low-crosstalk polymeric AWG-based tunablefilter operating around 1.55 μm

A wavelength tunable optical filter is a beneficial optical component for dense wavelength-division-multiplexed systems. We report a high-performance polymeric arrayed-waveguide grating (AWG)-based tunable filter made of cross-linked silicone and operating around 1.55 μm. This filter exhibited a TE-TM polarization shift of <0.03, a crosstalk of <-35 dB, an insertion loss of <3 dB, and an 8.8-nm tuning range in the 25°C-75°C temperature region     

Optical low coherence method for characterizing silica-basedarrayed-waveguide grating multiplexers

We describe a powerful method for the precise measurement of optical path phase errors and power-distribution coefficients in silica-based arrayed-waveguide grating multiplexers through the use of Fourier transform spectroscopy. The theoretical accuracies for measuring these parameters are ±1° and ±5%, respectively, when the geometrical step increment of the arrayed waveguides is greater than 48 μm. The method reveals the random distributions of optical path phase errors in two multiplexers with channel spacings of 100 and 10 GHz, and proves that these distributions are the main origins of the channel crosstalk. The method predicts that when optical path phase errors are sufficiently reduced, the channel crosstalk values will decrease to -39 and -29 dB, respectively, and these limits are due to slightly deformed power distributions     

Technique for widening passband of wavelength router

A new method to broaden the passband of arrayed-waveguide grating routers is proposed. A sinc(x) intensity distribution is formed in the array by a slot etched in the input star coupler. A 3 dB bandwidth of 65 GHz is obtained for a 100 GHz channel spacing and the adjacent channel crosstalk is less than 25 dB.     

10 GHz-spaced arrayed-waveguide grating multiplexer withphase-error-compensating thin-film heaters

An arrayed-waveguide grating multiplexer with thin-film heaters is fabricated to compensate for phase errors in arrayed waveguides. The phase errors are measured by Fourier transform spectroscopy with a low-coherence interferometer and are used as a monitor when we adjust the phases by controlling thin-film heaters. A channel crosstalk of -25 dB and a loss of 4.2 dB are achieved in a 5×5 10 GHz-spaced multiplexer     

Crosstalk reduction in arrayed-waveguide grating multiplexer/demultiplexer using cascade connection

This paper proposes a cascade-connected arrayed-waveguide grating (AWG) as a solution to the problem of crosstalk accumulation in a large-scale AWG multiplexer/demultiplexer (MUX/DEMUX) and demonstrates a 64-channel cascaded AWG module with a very low background crosstalk of less than -80 dB and a total crosstalk of about -34 dB. In this paper, the authors densely integrate 64 additional compactly designed crosstalk-suppressing AWGs whose bandwidths were carefully optimized and directly attach them to a conventional 64-channel AWG. Consequently, in addition to a very low crosstalk, a low insertion loss and a compact size without passband shape distortion are achieved with this module. Based on the performance of the cascaded AWG module, it is then estimated that it is possible to realize a 1000-channel AWG MUX/DEMUX that is free from the problem of crosstalk accumulation.     

Arrayed-waveguide grating multiplexer with loop-back optical pathsand its applications

We present a basic configuration of an unique integrated-optic arrayed-waveguide grating (AWG) multiplexer with loop-back optical paths and demonstrate an add-drop multiplexer (ADM), a network access terminal, and a wavelength channel selector for dense-WDM ring or bus networks, as three useful examples of its attractive applications. A key device in these components is a silica-glass based 1.55 μm polarization-insensitive 32×32 AWG multiplexer chip with 0.8 nm channel spacing which is fabricated using planar lightwave circuit (PLC) technologies. Fine operation in their new functional components is achieved by using the AWG multiplexer module having low insertion loss of 3.9 dB and low interchannel crosstalk of less than -28 dB     

Crosstalk Reduction in a Shallow-Etched Silicon Nanowire AWG

We introduced shallow-etched silicon nanowire into the arrayed waveguides to decrease the random phase error due to the core width fluctuation. A fairly improved crosstalk value of 18 dB was achieved in the fabricated arrayed-waveguide grating with the on-chip loss of 3 dB.      

400-channel arrayed-waveguide grating with 25 GHz spacing using1.5%-Δ waveguides on 6-inch Si wafer

A large-scale arrayed-waveguide grating with a 400-channel and 25 GHz spacing using 1.5%-Δ silica-based waveguides on a 6-inch Si wafer has been realised. Good demultiplexing properties have been obtained over the full Cand L-band range with an on-chip loss of 3.8 to 6.4 dB and a far-end crosstalk of -30 dB     

Wavelength multiplexer based onSiO2-Ta2O5 arrayed-waveguide grating

The characteristics of a wavelength multiplexer based on an arrayed-waveguide grating are carefully investigated by using the grating theory and related experiments. A 28-channel multiplexer is designed and fabricated as SiO₂-Ta₂O₅ waveguides on a 1 cm×2 cm substrate. The designed wavelength channel spacing of 1 nm is obtained. The crosstalk to an adjacent channel is -15 dB. The measured minimum loss is 4.2 dB, which is composed of 3.4 dB excess loss and 0.8 dB grating loss     

Narrow-channel-spacing 32-channel AWG multiplexer with an innovative alignment method

A 32-channel 50 GHz spaced arrayed-waveguide grating（AWG） with our innovative configuration has been designed and fabricated. The performance of the device has been fully tested by using a system that consists of a tunable laser light source （TLS）, an optical power meter and a polarization controller. The insertion loss （IS） of the device is 4.2-7.4 dB. The crosstalk is about - 28 dB. The IS uniformity is less than 3.3 dB. With our configuration,the performance of the device has been enhanced effectively and the difficulty in alignment process has been decreased obviously.     

The role of photomask resolution on the performance ofarrayed-waveguide grating devices

The crosstalk performance of an arrayed-waveguide grating (AWG) multiplexer or demultiplexer is primarily caused by random optical phase errors introduced in the arrayed waveguides. Because the layout of waveguides on a wafer is patterned via photomask through the photolithography process, the resolution of a photomask has a direct influence on the phase errors of an AWG. The paper presents a theoretical analysis on the phase error caused by photomask resolution and other basic design parameters. Both calculation and measurement results show that a high-resolution photomask (better than 25 nm) is a critical requirement to produce low-crosstalk (less than -30 dB) AWG demultiplexers. We also investigate the effect of nonideal power distribution in the arrayed waveguides because it contributes considerable phase errors when material impurity is not well controlled during wafer fabrication. Basic criteria of power profile truncation, number of grating waveguides, and material index variation are also summarized     

Fabrication of 64×64 arrayed-waveguide grating multiplexer onsilicon

A 64 channel arrayed-waveguide multiplexer with 0.4 nm (50 GHz) channel spacing at 1.55 μm has been fabricated using SiO₂-Si waveguides. The authors obtained a crosstalk of less than -27 dB to neighbouring and all other channels. The on-chip insertion loss ranges from 3.1 to 5.7 dB for central and peripheral output ports, respectively     

Very low insertion loss arrayed-waveguide grating with verticallytapered waveguides

We propose and demonstrate a very low insertion loss silica-based arrayed-waveguide grating (AWG) achieved using a novel structure, which has vertically tapered waveguides between arrayed-waveguides to reduce the slab-to-arrayed-waveguide transition loss. A spot-size converter is also incorporated in the AWG to reduce the fiber-to-waveguide coupling loss. The structure can be formed by a process involving the conventional photolithography and reactive ion etching. The structure provided a loss reduction of 1.5 dB. Moreover, we have successfully obtained a minimum insertion loss of 0.75 dB with a crosstalk of -40 dB and polarization-independent operation     

用于单片集成的InP阵列波导光栅设计和制备

InP 阵列波导光栅(AWG)是InP 基单片多波长转换器中的重要单元。采用深脊型波导结构,设计了一种10通道、通道间隔200GHZ(1.6nm)的偏振无关型InP基阵列波导光栅。采用外延技术、光刻、感应耦合等离子体刻蚀技术等在实验室制造出了这种AWG。经过测试,插入损耗约为-8dB,串扰小于-17dB,中心通道和旁边通道的通道均匀性基本上在3dB左右。     

Optical demultiplexer using concave grating in 0.7?0.9 ?m wavelength region

Experimental results of a demultiplexer using an aberration corrected concave grating for an optical system are described. The demultiplexer has 10 channels and a wavelength spacing of 20 mm from 0.7 to 0.9 ?m wavelengths. Insertion losses and crosstalk were less than 2.5 dB and -30 dB, respectively, for all channels.