Optical transmitter

Details Optical transmitter Optical transmitter

1999-01-25

2001-12-25

Negash, Kinfe-Michael (Department: 2633)

Optical: systems and elements

Deflection using a moving element

Using a periodically moving element

C359S199200, C359S199200, C359S199200

Reexamination Certificate

active

06333803

ABSTRACT:

TECHNICAL FIELD
The present invention relates to optical transmitters applied in the field of optical communication and, more particularly, to optical transmitters which are useful for wavelength-division multiplexed(WDM) optical communication system.
BACKGROUND OF THE INVENTION
A prior art optical transmitter used for the wavelength-division multiplexed optical communication system has a construction as shown in
FIG. 14
, comprising a plurality of semiconductor lasers A of different oscillation wavelengths, the optical outputs of which are independently modulated either directly or externally for wavelength-multiplexed optical transmission. Up to date, an optical transmitter using a Fabry-Perot resonator or like optical resonator also has been developed. The optical resonator in this optical transmitter converts light from a light source to multiple mode light, which has a regular wavelength spacing and is modulated independently by a plurality of external modulators for the wavelength-multiplexed optical transmission.
In the wavelength-division multiplexed optical communication system, a bandwidth limitation to a range centered on the wavelength of 1,550 nm is imposed on an optical amplifier, which relays optical signal. For mass communication by providing a large number of optical signals in the limited range, it is necessary to prevent isolation deterioration of adjacent optical signal transmitted from the optical transmitter in long use by accurately controlling the optical signal wavelengths. However, in order to preclude wavelength variations due to the wavelength isolation deterioration and ensure stable oscillation wavelength of the light source semiconductor laser such as to meet the above requirements, highly advanced techniques are required, giving rise to an optical transmitter price increase. In the optical transmitter using the optical resonator, it is possible to use a semiconductor laser, which is subject to wavelength variations, as the light source without giving rise to the problem of the wavelength isolation deterioration. This is so because multiple mode light, which is free from wavelength variations and is modulated, can be obtained from the laser beam by a resonating action of an optical resonator. However, the multiple mode light generated by the optical resonator is peculiar thereto. This is undesired form that the standpoint of the free wavelength setting. For instance, it is difficult to set non-uniformly spaced-apart channels.
SUMMARY OF THE INVENTION
An optical transmitter according to the invention as set forth in claim
1
is, as shown in
FIGS. 1 and 2
, comprises a supercontinuum light source which is composed of an optical amplifier made by using a constant polarized wave amplification fiber and a constant polarized wave fiber which has a length of at least a specified value, is connected to the output side of the optical amplifier and emits light having a continuous wave and a stable plane of polarization, a constant polarized wave optical demultiplexer which takes out a light with a desired wavelength from the continuous wave light, and an external modulator which superposes desired information upon the light with the desired wavelength.
An optical transmitter according to the invention as set forth in claim
2
, is the optical transmitter as set forth in claim
1
, in which the constant polarized wave amplification fiber and/or the constant polarized wave optical fiber are/is of a dispersion shift type or a dispersion flat type.
An optical transmitter according to the invention as set forth in claim
3
, is the optical transmitter as set forth in claim
1
, in which continuous light is inputted as source light to the supercontinuum light source.
An optical transmitter according to the invention as set forth in claim
4
, is the optical transmitter as set forth in claim
2
, in which continuous light is inputted as source light to the supercontinuum light source.
An optical transmitter according to the invention as set forth in claim
5
, is the optical transmitter as set forth in each of claims
1
to
4
, in which light other than single-frequency (or single-wavelength) light is inputted as source light to the supercontinuum light source.


REFERENCES:
patent: 5729372 (1998-03-01), Terahara et al.
patent: 5963567 (1999-10-01), Veselka et al.
patent: 6081355 (2000-06-01), Sharma et al.
patent: A-4-281631 (1992-10-01), None
patent: A-4-306928 (1992-10-01), None
patent: A-5-224252 (1993-09-01), None
patent: A-7-264166 (1995-10-01), None
patent: A-8-18540 (1996-01-01), None
patent: A-8-29814 (1996-02-01), None

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