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Tunable Optical Transmitter Not Requiring Switched Or Tunable Lasers

IP.com Disclosure Number: IPCOM000101981D
Original Publication Date: 1990-Oct-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Green, PE: AUTHOR

Abstract

In a wavelength division lightwave network, either the transmitter, the receiver, or both, must be wavelength-tunable. There are many reasons that a tunable transmitter is particularly desirable, but the conventional solution, a tunable laser, suffers from the disadvantage that the only easily available ones tune too slowly, since the tuning is mechanical.

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Tunable Optical Transmitter Not Requiring Switched Or Tunable Lasers

       In a wavelength division lightwave network, either the
transmitter, the receiver, or both, must be wavelength-tunable. There
are many reasons that a tunable transmitter is particularly
desirable, but the conventional solution, a tunable laser, suffers
from the disadvantage that the only easily available ones tune too
slowly, since the tuning is mechanical.

      The present invention gets around this problem by combining
three technologies that are widely available, (1) a broad-spectrum
(1) light- emitting diode (LED) which is ON-OFF modulated by the bit
stream, (2) a tunable acousto-optic (2) (or any other kind of
fast-acting) filter, which passes only a small fraction of the LED
radiation, namely that at or close to a single wavelength, and (3) a
broadband photonic amplifier (e.g., an optically pumped erbium-doped
fiber co-doped with alumina (3)), which recovers the loss of signal
energy that has occurred because only a small portion (e.g., 10-3) of
it is at the useful wavelength region.

      One example of an acousto-optic filter is an acousto-optic
deflector followed by an exit slit.

      There are several advantages to this approach: (1) The
components are available today,  (2) The tunability is rapid, since
the retuning time is given by the acoustic propagation time of the RF
signal applied to the acousto-optic crystal as it propagates sideways
across the optical beam. ...