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Mode-Locked Laser for Wavelength Division Multi-Access Network

IP.com Disclosure Number: IPCOM000034724D
Original Publication Date: 1989-Apr-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 4 page(s) / 118K

Publishing Venue

IBM

Related People

Dono, NR: AUTHOR [+2]

Abstract

A technique is described whereby a mode-locked laser for wavelength division multi-access networks generates the desired spectral comb of wavelengths in one operation. The concept simplifies previously described centralized wavelength division multi-access networking by replacing a large number of individual lasers with the mode-locked laser. The concept described herein is designed to be used in a number of wavelength division multi-access (WDMA) applications. It is particularly relevant to a centralized architecture, which not only centralizes most functions, but adds several methods of performing coherent homodyne detection. (Image Omitted) In a typical WDMA network, as shown in Fig. 1, each terminal transmitter sends on a different wavelength (under the command of the controller).

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Mode-Locked Laser for Wavelength Division Multi-Access Network

A technique is described whereby a mode-locked laser for wavelength division multi-access networks generates the desired spectral comb of wavelengths in one operation. The concept simplifies previously described centralized wavelength division multi-access networking by replacing a large number of individual lasers with the mode-locked laser. The concept described herein is designed to be used in a number of wavelength division multi-access (WDMA) applications. It is particularly relevant to a centralized architecture, which not only centralizes most functions, but adds several methods of performing coherent homodyne detection.

(Image Omitted)

In a typical WDMA network, as shown in Fig. 1, each terminal transmitter sends on a different wavelength (under the command of the controller). Each receiver receives the desired transmission by tuning to the correct wavelength in the local tunable optical filter, just prior to photodetection. The star coupler serves the function of merging and then broadcasting all of the transmissions. In a fully centralized WDMA network, as shown in Fig. 2, the lasers and the tunable receivers are moved into the central hub [1]. Each transmitter consists of a modulator of light intensity, rather than a laser whose output is electrically modulated. An extra fiber is run from the hub to each terminal, so as to carry the unmodulated light to feed each station's modulator. The centralized version has desirable attributes in that a common temperature environment is present for all lasers and filters and a cost savings can be realized by arraying the lasers.

(Image Omitted)

However, there is a distinct disadvantage to the centralized approach in that the many individual lasers require stabilization at the equidistant points on the wavelength axis. Therefore, the concept described herein concentrates on this disadvantage by replacing the many individual lasers with a mode-locked single laser. The mode-locked single laser implementation is performed by substituting the "n" lasers with separately fixed-tuned lasers in a single mode-locked laser, followed by "n" narrowband optical filters [2], as shown in Fig. 3. Mode-locking is produced by exciting a...