Optical delay time adjuster and optical time-division...

Details Optical delay time adjuster and optical time-division... Optical delay time adjuster and optical time-division...

1999-02-11

2001-04-10

Palmer, Phan T. H. (Department: 2874)

Optical waveguides

Accessories

External retainer/clamp

C385S024000, C359S199200, C250S227120

Reexamination Certificate

active

06215941

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an optical delay time adjuster that can be employed in an optical time-division multiplexer.
BACKGROUND OF THE INVENTION
A conventional optical time-division multiplexer is described, for example, in Proceedings of the 1994 Spring Conference of the Institute of Electronics, Information and Communication Engineers, pp. 4-443-4-444. An optical time-division multiplexer described in this publication has two optical fibers, including an optical delay generator and an optical coupler. The two optical fibers connect two input ports of the multiplexer with the optical coupler. One of the two optical fibers is longer than the other one so that there is a delay in the arrival at the coupler of a signal in the longer fiber relative to the arrival of a signal in the shorter fiber;
In a conventional optical time division multiplexer, the delay time depends upon the lengths of optical fibers. However, the length of optical fibers expand or contract according to the surrounding temperature. Thus, the delay time also depends on the temperature. Therefore, a variation in the temperature will change the delay time and may thus introduce errors into the operation of a conventional optical time-division multiplexer, or any other device which relies upon the length of optical fibers to create a time delay.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide an optical delay time adjuster which generates a controllable time delay, and an optical time-division multiplexer that includes the same.
According to the invention, the optical delay time adjuster includes an optical fiber and a means for adjusting the length of the fiber. In some embodiments, the delay time adjuster includes a support, an optical fiber attached to the support, and a heater or a cooling device such as a thermoelectric element attached to the support for changing the temperature of the support and thereby the optical fiber. By heating or cooling the optical fiber, the heater or cooling device controls the length and refractive index of the optical fiber, to thereby control the optical delay time provided by the optical fiber.
In another embodiment, the optical delay time adjuster includes a piezoelectic element. By applying a voltage to a piezoelectric element about which the optical fiber is wound, the fiber is mechanically stretched to increase the length and thereby the delay time according to the applied voltage.


REFERENCES:
patent: 5111322 (1992-05-01), Bergano et al.
patent: 5703708 (1997-12-01), Das et al.
Satoki Kawanishi and Masatoshi Saruwatari. “Time-division-multiplexed 100 Gbit/s optical transmission technology”. Proceedings of the 1994 IEICE Spring Conference, Mar. 26-29, 1994, pp. 4-443-4-444.

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