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Cost Effective Fiber Laser Transmitter for WDMA

IP.com Disclosure Number: IPCOM000108018D
Original Publication Date: 1992-Apr-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 81K

Publishing Venue

IBM

Related People

Bhathena, F: AUTHOR [+4]

Abstract

Recently, considerable progress has been made in Wavelength Division Multiple Access computer networking. The cost of the components, in particular, the single frequency emitting laser diode used for transmission, limits extensive commercial application of the WDMA network. Here, we propose a combination of Erbium-doped fiber lasers, gratings, and external modulators as the laser transmitters in a WDMA network. The output from each individual fiber laser can be used to support many users, thus lowering the cost.

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Cost Effective Fiber Laser Transmitter for WDMA

       Recently, considerable progress has been made in
Wavelength Division Multiple Access computer networking.  The cost of
the components, in particular, the single frequency emitting laser
diode used for transmission, limits extensive commercial application
of the WDMA network.  Here, we propose a combination of Erbium-doped
fiber lasers, gratings, and external modulators as the laser
transmitters in a WDMA network.  The output from each individual
fiber laser can be used to support many users, thus lowering the
cost.

      The figure shows the proposed design in which the feedback of
the Er3+ doped fiber laser is provided by a Fabry-Perot filter as the
wavelength selective element.  The periodic transmission of the
Fabry- Perot filter allows lasing occurring at those wavelengths.
The output of the fiber laser is fed into a reflective or refractive
grating in which individual lasing modes are decoupled.  An external
modulator is then used to encode the data signal onto the light beam
as shown.

      The thickness of the Fabry-Perot filter determines the lasing
mode (channel) spacing.  By choosing the thickness to be around 1 mm
and a reflectivity of 0.97, we could have channels separated by 7 o
and the filter passband of 0.07 o (about 89 MHz).  Grating of
resolution of Z 1 nm could be easily achieved by a commercial 1/4 m
reflective grating (800 lines/mm). However, an important feature is
the lasing modes in the fiber laser has to be controlled.  Recent
experiments show that there is considerable beating noise due to
existence of several lasing modes Z 6 MHz apart supported by the Z...