Sensitivity penalty in multichannel coherent optical communications

The error rates and sensitivity penalties for multichannel coherent optical communications systems are evaluated for amplitude-shift keying (ASK), phase-shift keying (PSK), and frequency-shift keying (FSK) modulation, taking into account adjacent channel interference. Both time-domain and frequency-domain analysis are used, the latter being based on a Gaussian approximation. Both techniques yield similar results for sensitivity penalties below 1 dB. For FSK systems, larger values of the modulation index Δ do not necessarily lead to larger channel spacings. ASK and PSK systems both require larger channel spacings than FSK systems with Δ=1. The study was conducted for sources with linewidths narrow enough so that phase noise does not degrade the performance of receivers with matched filter demodulators     

Non-Recursive adaptive impulse noise canceller

A non-recursive adaptive impulse noise canceller (AINC) is investigated. The AINC is designed to suppress long impulsive interferences which are a primary source of errors in many communication systems. Performance of the AINC depends upon the input filter of the receiver. It is shown that the optimum input filter is LPF; the optimum LPF bandwidth exists which provides the minimum error rate of the receiver. The system error rate is studied by means of a computer simulation. Simulation results indicate that the AINC provides a very effective suppression of impulse noise. However, conditions in a real communication channel may be quite different from those chosen for simulation. Therefore, further research remains to be done before the AINC can be recommended for practical applications.     

Combined frequency and amplitude modulation for the STARNET WDMcomputer communication network

STARNET is an experimental wavelength-division multiplexed computer communication network that makes use of combined modulation of a single transmitter laser to implement a virtual-ring control sub-network and a reconfigurable high-speed sub-network over a passive star architecture. In this letter, we demonstrate a new technique of combined modulation that works by direct frequency-shift keyed (FSK) modulation and external amplitude-shift keyed (ASK) modulation of a semiconductor laser. By adjusting the amplitude modulation depth to 0.8, both the 125 Mb/s ASK receiver and the 1.244 Gb/s FSK receiver operate with equal bit-error ratios less than 10^-9 for a received signal power of -24 dBm     

High-nonlinearity fiber optical parametric amplifier with periodicdispersion compensation

Theory shows that the maximum gain and bandwidth of one-pump fiber optical parametric amplifiers made from high-nonlinearity fiber, operated with a pump wavelength λ_p far from the fiber zero-dispersion wavelength λ₀ can greatly be improved by periodic dispersion compensation. We have performed experiments and obtained good agreement with theory: for λ_p=1542 and λ₀=1591 nm, we have increased the bandwidth from 7 to 28 nm, and the maximum gain from 15 to 20 dB, by splicing three pieces of standard fiber at regular intervals in a 40-m long nonlinear fiber     

Impact of crosstalk in an arrayed-waveguide router on an opticaladd-drop multiplexer

The impact of crosstalk in an arrayed-waveguide (AWG) router on the performance of an N-channel optical add-drop multiplexer (OADM), with m add/drop channels and n-pass channels is theoretically investigated. A single arrayed-waveguide router is simultaneously used for multiplexing and demultiplexing. This results in crosstalk not only from the incoming channels, but from the outgoing channels as well. We show that the performance of the OADM degrades as either N or m are increased, suggesting that the number of channels in a network based on OADM's is limited by crosstalk in the AWG router. When an optical filter is added at the output of the OADM the digital signal-to-noise ratio Q is independent of N and m, and within a few tenths of a decibel of the perfect filtering case     

200-nm-bandwidth fiber optical amplifier combining parametric andRaman gain

Theory shows that the gain bandwidth of a one-pump fiber optical parametric amplifier (OPA) using highly nonlinear fiber (HNLF) could be more than 200 nm. Under these circumstances, the OPA gain would overlap the pump-induced Raman gain. We have studied the combined effects of OPA and Raman gain theoretically and experimentally. The experimental results demonstrate a 200-nm bandwidth from a single fiber-optical amplifier and also verify that the influence of the Raman effect is relatively small, as predicted by the theory     

All-optical 3R regeneration technique using injection-locking ingain-switched DFB-LD

A new all-optical 3R regeneration technique using injection-locking in a gain-switched DFB-LD is proposed. The operation of the technique is confirmed numerically and experimentally. Both simulation and experimental results show that the degraded RZ pulses are reshaped, retimed, and regenerated by injection-locking, into short pulses generated by gain-switching. Moreover, error-free all-optical 3R regeneration at 2.5 Gbit/s has been successfully achieved, with 1.5 dB negative penalty     

Optical Burst Transport: A Technology for the WDM Metro Ring Networks

We propose a sublambda traffic-grooming scheme on wavelength-division-multiplexing ring networks, named optical burst transport. The network protocol and architecture are designed to support dynamic bandwidth allocation, which is more reasonable for bursty data traffic. To verify our network protocol and architecture, we build a testbed which supports burst-mode transmission. Also, we transmit streaming video over Ethernet as an application