JPS58119241A - Optical signal detector - Google Patents

Abstract

PURPOSE:To detect optical signals with high sensitivity and to receive a weak signal in a high speed, by amplifying light with an induced scattering and amplifying medium. CONSTITUTION:The wavelength of an input light is denoted as 1.38mum. The input light inputted through a coupling optical system 4 is synthesized with an output light of a YAG laser 1 of 1.32mum at an optical synthesizer 3 and led to an optical fiaber 5. The induced scattering band of the optical fiber 5 to the 1.32mum light is taken as 1.36-1.40mum. The optical fiber 5 amplifies the transmitted optical signal with the induced scattering amplification and generates a wavelength conversion amplified signal light. Each optical signal is branched at a diffraction grating optical demultiplexing device 6 and each component is detected at photodetectors 7, 8. The correlation of the output signals of the sections 7, 8 is taken, the noise component is reduced and the signal detection with high sensitivity is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical signal detection device that can detect optical signals at high speed and with high sensitivity.

Conventionally, as a detection device for a weak high-speed pulse optical signal, a device using a photodiode or an avalanche photodiode as a detection element has been used. In particular, avalanche photodiodes are increasingly being used in optical fiber communication equipment that requires the reception of high-speed, weak signals. Avalanche photodiodes have an internal amplification effect.

Although highly sensitive optical signal detection is possible, the internal amplification is only several tens of times at most, and detection of weak signals requires combined use with a low-noise electrical amplifier.

For this reason, there was a limit to the improvement in sensitivity. On the other hand, although photodiodes are capable of relatively high-speed optical signal detection, they have the disadvantage that their applications are limited due to their low detection sensitivity.

An object of the present invention is to provide an optical signal detection device that eliminates the above-mentioned drawbacks.

According to the present invention, there is provided an optical multiplexer that multiplexes an input optical signal and pump light from a pump light source, a stimulated scattering amplification medium connected to the optical multiplexer, and an optical multiplexer connected to the stimulated scattering amplification medium. An optical signal detection device is obtained, which includes a wave splitter and a signal processing unit for the amplified signal component and the wavelength-converted amplified signal component output from the optical demultiplexer.

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing one embodiment of the present invention. This example uses a 1.32 μm YAG laser L as an excitation light source,
1. Optical multiplexer containing a dielectric multilayer reflective film for light of 32 μm inside. 13 μm band zero-weighted mode optical fiber 51 as stimulated scattering amplification medium 6. Diffraction grating optical demultiplexer 6. G
e Photodetectors 7, 8 using photodiodes as detection elements.
It is composed of a correlation detection section 9 and coupling optical systems 2 and 4.

Now, the wavelength 1.38 which is light within the stimulated scattering band 1436 to 1.40 μm for optical fiber 501.32 μm light.
An optical signal of .mu.m is introduced through a coupling optical system 4, combined with light from a YAG laser 1 by an optical multiplexer 3, and guided through an optical fiber 5. The optical signal component is amplified by the stimulated scattering amplification effect of the optical fiber 5, and at the same time, by optical mixing of the amplified signal light and the pumping light, the optical signal component has almost the same intensity as the amplified signal light and is shorter than the pumping light. Wavelength conversion of the wavelength produces an amplified signal component.

When the frequency of the pumping light is νp%, the frequency of the signal light is σS, and the frequency of the wavelength-converted amplified signal light is νC, there is a relationship: σ=sip-(ss-sip). The amplified signal component, the wavelength-converted amplified signal component, and the transmitted pump light component are demultiplexed by a diffraction grating optical demultiplexer 6, and both signal components are detected by photodetectors 7 and 8, respectively. Since both signal components change according to the input signal, by detecting the correlation between the two output signals of the photodetector 7 and 80, the uncorrelated noise component ratio generated in the photodetectors 7 and 8 is reduced, resulting in high sensitivity. This enables accurate signal detection. In this example, which uses stimulated scattering amplification, the amplification is entirely in the optical domain.
In other words, due to interaction between photons, extremely high speed,
For example, pulse signal amplification in the 1OGb/s region is possible, and an amplification degree of 104 to 105, which is difficult to achieve with electronic devices, can be obtained relatively easily. Note that the photodetector 7.8 may be configured to detect the intensity of the entire spectrum of the signal, but it also detects the spectral shapes of the amplified signal component and the wavelength-converted amplified signal component, so that both of them are located at the excitation light spectral position. By performing the nine-correlation detection process in consideration of the fact that it has a symmetrical shape around the center, background noise components can be more effectively reduced and signal detection with high sensitivity can be achieved.

By the way, in the above embodiment, the excitation light source is a YAG laser, but the present invention is not limited to this, and can be appropriately selected depending on the wavelength of the signal light. For example, an Ar ion laser can be used. You may do so. I lost my head. The optical signal is not necessarily limited to a single wavelength as in the above embodiment, but may be a combination of a plurality of mutually independent optical signals using a plurality of wavelengths.

Finally, to summarize the features of the present invention, it is possible to obtain a low-noise optical signal detection device capable of high sensitivity and high-speed response.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment based on the present invention. In the figure, 1... YAG laser, 2 and 4...
...Coupling optical system, 3... Optical multiplexer, 5...
...Optical fiber, 6...Diffraction grating optical demultiplexer%7
and 8...river/light detection section, 9...correlation detection section.

Claims (2)

[Claims] (1) An optical multiplexer that combines the input optical signal and the pump light from the pump light source, a stimulated scattering amplification medium connected to the optical multiplexer, and a nine optical demultiplexer connected to the stimulated scattering amplification medium. An optical signal detection device comprising: and a signal processing section for an amplified signal component and a wavelength-converted amplified signal component output from the optical demultiplexer. (2) The optical signal detection device according to claim 1, wherein the signal processing section has a correlation detection function.