Multichannel laser transmitter with a single output port

Details Multichannel laser transmitter with a single output port Multichannel laser transmitter with a single output port

1998-11-16

2001-05-29

Kim, Robert H. (Department: 2877)

Coherent light generators

Particular active media

Gas

C372S020000, C372S026000, C385S015000, C385S017000, C385S037000, C385S046000

Reexamination Certificate

active

06240118

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
Related subject matter is disclosed in the concurrently filed application entitled “LASER TRANSMITTER BASED ON A COUPLER AND HAVING A SEPARATE OUTPUT PORT” by the same inventors, C. R. Doerr and C, H. Joyner, both applications being assigned to the same Assignee.
TECHNICAL FIELD OF THE INVENTION
This invention relates to lasers and, more particularly, to a multichannel laser having a single output port, as well as an improved method of controlling the output of optical signals from a multichannel laser.
BACKGROUND OF THE INVENTION
To make optimal use of the bandwidth available in a fiber based network, it is desirable to use as many separately detectable wavelength channels as possible and to encode data onto each wavelength at as high a speed as possible. One problem with lasers that deliver multiple channels is that the cavity length for many of them is long, making direct modulation above 1 GHz impractical due to the round trip time of a photon in the cavity. A possible solution is to use an output power tap on the main laser cavity and to modulate this output while the main laser cavity runs in continuous wavelength mode. (see C. H. Joyner et. al. “An 8 channel digitally tunable transmitter with electroabsorbtion modulated output by selective-area epitaxy” PTL vol. 7, no.9, September 1995 pp. 1013-1015 or the pending patent application entitled “Improved tunable transmitter with Mach-Zehnder Modulator,” Ser. No. 09/016,176, filed on Jan. 30, 1998 by C. H. Joyner. In both of the above cases the modulator was external to the laser cavity.
For improved modulation rates at low drive levels, it is desired is to integrate a phase modulator capability into a laser transmitter. Moreover, in WDM applications it would also be desirable to combine a number of these integrated modulated lasers together into a single multichannel modulated laser.
SUMMARY OF THE INVENTION
In accordance with the present invention, a multichannel laser is based on an interleaved chirped waveguide grating router. An interferometric modulator is incorporated inside a laser cavity by means of a waveguide grating router and enables independent modulation or switching of any of the wavelengths of the multichannel laser. The interferometric modulator operates independently of the wavelength selection elements of the waveguide grating router used to select the frequencies of the multichannel laser.
More particularly, in accordance with the present invention, a multichannel laser comprises a waveguide grating router including a first star coupler, a second star coupler, and three interleaved sets of m waveguide grating arms (where m is a number greater than one) interconnecting to a first side of the first and second star couplers, for producing n wavelengths in the multichannel laser (where n is a number greater than one). A second side of the first coupler includes a first connection to a reflecting surface, and a second connection to an output port. A second side of said second coupler includes a first group of n connected waveguides, each of the n waveguides connected through an optical amplifier to a reflecting surface, a second group of n connected waveguides, each of the n waveguides connected through an optical amplifier and a controllable phase shifter to a reflecting surface. A laser signal is generated in each of n cavities formed by one of the first group of waveguides, the first and second couplers, the group of m waveguide grating arms, and the first connection of said first coupler. The magnitude of each of the n laser signals appearing at the output port are controlled by the optical amplifier and phase shifter in each one of the second group of n connected waveguides.


REFERENCES:
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“An 8 channel digitally tunable transmitter with electroabsorbtion modulated output by selective-area epitaxy” IEEE Phot. Tech. Let. vol. 7, No. 9, Sep. 1995 pp. 1013-1015 by Joyner et. al.
“Optimum design of a planar array of tapered waveguides,” published in J.Opt.Soc. Am. A, vol. 7, No. 11, Nov. 1990 by C. Dragone.
U.S. application No. 09/016,176, Joyner et al., filed Jan. 30, 1998.

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