T. Healy

Multi-wavelength source using low drive-voltage amplitude modulators for optical communications

A simple and cost-effective technique for generating a flat, square-shaped multi-wavelength optical comb with 42.6 GHz line spacing and over 0.5 THz of total bandwidth is presented. A detailed theoretical analysis is presented, showing that using two concatenated modulators driven with voltages of 3.5 V(pi) are necessary to generate 11 comb lines with a flatness below 2dB. This performance is experimentally demonstrated using two cascaded Versawave 40 Gbit/s low drive voltage electro-optic polarisation modulators, where an 11 channel optical comb with a flatness of 1.9 dB and a side-mode-suppression ratio (SMSR) of 12.6 dB was obtained.

Dispersion tolerance of coherent WDM

We present the transmission of a 298.2-Gb/s copolarized coherent wavelength-division-multiplexing system over 80 km of standard single-mode fiber, achieving an information spectral density of 1 b/s/Hz with no prefilters at the transmitter. Odd and even tributary channels were encoded with data and delayed-data-bar pseudorandom binary sequence 27-1 patterns. The dispersion tolerance is investigated, and the dispersion penalty of this system is improved through adjustment of the relative phase of adjacent channels. Under optimum conditions, the dispersion penalty could be reduced from over 3 dB to less than 1 dB

Towards 1TbE using Coherent WDM

In this paper we report the transmission properties of a 0.3 Tbit/s coherent WDM signal and confirm the scalability of this signal to 0.6 Tbit/s using polarisation division multiplexing.

Coherent WDM: the achievement of high information spectral density through phase control within the transmitter

We review a new transmission technique, coherent WDM, which allows high information spectral density to be achieved in a simple and low-cost configuration using phase control at the transmitter.

0.6Tbit/s Capacity and 2bit/s/Hz Spectral Efficiency at 42.6Gsymbol/s Using a Single DFB Laser with NRZ Coherent WDM and Polarisation Multiplexing

The capacity of a single-source coherent WDM (CoWDM) system is doubled from 298.2 Gbit/s to 596.5 Gbit/s by introducing polarisation multiplexing (PolMUX). This is achieved by generating a band of seven non-return-to-zero (NRZ) encoded channels at 42.6 Gsymbol/s. BER characterisations for single channel, 1 bit/s/Hz CoWDM channels and 2 bit/s/Hz CoWDM+PolMUX are performed. This work obtained high information spectral density of 2 b/s/Hz, allowing ISDs in excess of 1.8 b/s/Hz in a banded multi-Terabit/s system.

1 b/s/Hz coherent WDM transmission over 112 km of dispersion managed optical fibre

The performance advantage of using dispersion-managed fibre in coherent WDM systems is demonstrated. Limitations due to nonlinearity are no more severe for a 298 Gb/s coherent WDM signal than for an individual 42.6 Gb/s channel.

Phase stabilisation of coherent WDM modulator array

This paper reports for the first time a simple stabilisation circuitry technique to monitor and control the relative phase between adjacent channels in a coherent WDM transmitter, achieving optimum performance.

Flat 11 Phase-locked Channels Optical Comb Generator using Low-Drive Voltage Modulators

This paper proposes and experimentally demonstrates the use of cascaded polarisation mode converter based modulators for the generation of flat optical frequency combs, and have experimentally demonstrated an 11 line comb with a frequency spacing of 42.6 GHz.

Transmission Impairments for 298.2Gbit/s Coherent WDM over 600km of Standard Single Mode Fibre

Coherent wavelength division multiplexing (CoWDM) is a promising technique in order to achieve, in a simple and cost-effective configuration, high information spectral densities (ISD). This paper shows an estimation of the impact of non-linear effects (NLE) and polarisation mode dispersion (PMD) for a CoWDM system using standard single-mode fibre (SSMF), showing that this high ISD system offers similar total reach to a standard WDM system with 42.6Gbit/s NRZ channels. The impact of noise and NLE on a 298.2Gbit/s CoWDM system generated from seven 42.6Gbit/s random data streams (512 and 27-1 bits for simulated and experimental results respectively) was considered .

Optical multiplexing for high speed systems

In this paper we review the progress of optical multiplexing. In particular we compare the well known techniques of optical time domain multiplexing and wavelength division multiplexing, and introduce a new technique (coherent-WDM) which retains the advantages of both of these traditional technologies.