Generation of a widely spaced optical frequency comb using an amplitude modulator pair

Fatima C.Garcia Gunning*, Andrew D. Ellis

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review

Abstract

Multi-wavelength sources are required for wavelength division multiplexed (WDM) optical communication systems, and typically a bank of DFB lasers is used. However, large costs are involved to provide wavelength selected sources and high precision wavelength lockers. Optical comb generation is attractive solution, minimizing the component count and improving wavelength stability. In addition, comb generation offers the potential for new WDM architectures, such as coherent WDM, as it preserves the phase relation between the generated channels. Complex comb generation systems have been introduced in the past, using fibre ring lasers [1] or non-linear effects within long fibres [2]. More recently, simpler set-ups were proposed, including hybrid amplitude-phase modulation schemes [3-5]. However, the narrow line spacing of these systems, typically 17 GHz, restricts their use to bit rates up to 10 Gbit/s. In this paper, we propose and demonstrate a simple method of comb generation that is suitable for bit rates up to 42.667 Gbit/s. The comb generator was composed of two Mach-Zehnder modulators (MZM) in series, each being driven with a sinusoidal wave at 42.667 GHz with a well-defined phase relationship. As a result, 7 comb lines separated by 42.667 GHz were generated from a single source, when amplitude up to 2.2 Vx was applied to the modulators, giving flatness better than 1 dB. By passively multiplexing 8 source lasers with the comb generator and minimising inter-modulator dispersion, it was possible to achieve a multi-wavelength transmitter with 56 channels, with flatness better than 1.2 dB across 20 nm (2.4 THz).

Original languageEnglish
Article number74
Pages (from-to)469-473
Number of pages5
JournalProceedings of SPIE - The International Society for Optical Engineering
Volume5825
DOIs
Publication statusPublished - 3 Jun 2005
EventOpto-Ireland 2005: Optoelectronics, Photonic Devices, and Optical Networks - Dublin, Ireland
Duration: 4 Apr 20056 Apr 2005

Keywords

  • Comb source
  • High Speed Transmission
  • Optical communications
  • Phase control
  • Spectral efficiency
  • Wavelength division multiplexing

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