Optical: systems and elements – Optical frequency converter – Parametric oscillator
Patent
1992-05-18
1993-12-28
Moskowitz, Nelson
Optical: systems and elements
Optical frequency converter
Parametric oscillator
359341, 372 22, 385 1, G02B 626, G02F 135
Patent
active
052744957
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to an optical amplifier on the principle of optical parametric amplification or four-wave mixing optical amplification, and more particularly to an optical amplifier in which phase matching between signal light and pump light is easily achieved and, hence, effective optical amplification of the signal light can be obtained over a broad frequency band.
2. Description of the Related Art
Optical amplifiers of the type in which the amplitude of electric field of light is directly amplified are applicable to the following uses in the optical fiber transmission system, and of late, intense research on the optical amplifiers of this type is being made in various areas:
(A) Use for increasing optical output of a light source: By increasing the output of a light source of the signal light in an optical transmitter, the transmission distance can be increased. When the optical amplifier is used for the light source of local light in an optical receiver on a coherent optical wave communication system, the reception sensitivity can be improved.
(B) Use for a preamplifier in an optical receiver: By performing optical amplification in the stage immediately before the photoelectric conversion stage, the reception sensitivity can be improved.
(C) Use for an optical repeater: By the direct amplification of light, as compared with the method in a conventional optical repeater in which a light signal is once photo-electrically converted into an electric signal and then the electric signal is amplified, it becomes possible to make the repeater itself smaller in size and also to increase the repeater-to-repeater distance.
There has been known an optical amplifier in which optical parametric amplification of signal light is achieved by nonlinear effect of second order obtained when signal light and pump light are propagated through an optical waveguide structure made of a nonlinear optical material.
There has also been known an optical amplifier in which four-wave mixing optical amplification of signal light is achieved by nonlinear effect of third order obtained when signal light and pump light are propagated through an optical waveguide structure made of a nonlinear optical material.
However, such conventional optical amplifiers have had a disadvantage that phase matching between the signal light and the pump light is not always easily achieved therein and, hence, effective optical amplification of the signal light is obtained only within a narrow frequency band.
Accordingly, an object of the present invention is to provide an optical amplifier in which phase matching between the signal light and the pump light is easily achieved and, hence, effective optical amplification of the signal light can be obtained over a broad frequency band.
SUMMARY OF THE INVENTION
Viewed from an aspect, the present invention provides an optical amplifier adapted such that signal light and pump light are propagated through an optical waveguide structure therein having a core with a relatively high refractive index and a clad with a relatively low refractive index, at least the core exhibiting a nonlinear response of second order, to thereby achieve optical parametric amplification of the signal light, characterized by idler light attenuation means for attenuating idler light, which is generated in the process of optical parametric amplification, within the optical waveguide structure.
Viewed from another aspect, the present invention provides an optical amplifier adapted such that signal light and pump light are propagated through an optical waveguide structure therein having a core with a relatively high refractive index and a clad with a relatively low refractive index, at least the core exhibiting a nonlinear response of third order, to thereby achieve four-wave mixing optical amplification of the signal light, characterized by idler light attenuation means for attenuating idler light, which is generated in the process of four-wave mixing optical
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Fujitsu Limited
Moskowitz Nelson
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