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Method of Avoiding Tunable Lasers in a Coherent Wavelength Division Multiaccess Network

IP.com Disclosure Number: IPCOM000036415D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 6 page(s) / 154K

Publishing Venue

IBM

Related People

Dono, NR: AUTHOR [+2]

Abstract

Wavelength Division Multiaccess Network In a centralized wavelength division multiaccess network, tunable optical filters are used to feed each remote receiver with the desired transmitter's combined sum of a strong unmodulated light plus its weaker modulated signal, so as to allow the receiver to perform coherent homodyne detection over a wide tunablity range. Background

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Method of Avoiding Tunable Lasers in a Coherent Wavelength Division Multiaccess Network

Wavelength Division Multiaccess Network In a centralized wavelength division multiaccess network, tunable optical filters are used to feed each remote receiver with the desired transmitter's combined sum of a strong unmodulated light plus its weaker modulated signal, so as to allow the receiver to perform coherent homodyne detection over a wide tunablity range. Background

Fig. 1 shows the hub and receiver portion of a wavelength divi

(Image Omitted)

sion multiaccess (WDMA) network using a centralized architecture
1. This architecture has two disadvantages:

The tunablity range of the local oscillator is limited

to the 2-6 nm (out of a 200 nm band) range of today's

tunable lasers.

Each receiver portion requires an expensive tunable

laser.

The present article aims at removing these limitations. Fig. 1, WDMA network architecture, shows one terminal receiver and one receiver component. The centralized hub contains the tooth counting and local oscillator functions for each homodyne receiver. Solution

Fig. 2 shows the first of two steps in describing the proposed system. As with Fig. 1, only one terminal receiver component is shown. The upper optical star coupler broadcasts at all outputs an identical spectral comb of wavelengths, one wavelength corresponding to each laser whose signal is modulated by the remote transmitting terminals. The light in each tooth of this comb is unmodulated and relatively high powered. By contrast, the lower optical star coupler delivers to all outputs light of the same wavelengths but modulated and considerably weaker because it has traveled from hub to terminal and back again. Fig. 2 is the proposed simplified WDMA network (using centralization, tooth counting and homodyne detection).

The present architecture departs from the earlier one at this point. First, the light from the ith output of the upper star coupler is summed with the light from the ith output of the lower star. The result, for each of the N channels is a composite of two combs. Upon narrow band optical filtering of one of the teeth in this composite comb, it is seen that one has exactly the form of signal needed for remote homodyne detection, namely, a strong "local oscillator" signal lying exactly at the wavelength o...