JPH0537472A - Optical amplifier - Google Patents

Abstract

PURPOSE:To obtain a fixed amplitude without being affected by a wavelength by branching the output optical signal of an optical amplifier into the multiplexed optical signals of two wavelengths by a branching filter, passing the optical signal of the wavelength having a larger gain at the optical amplifier through an optical attenuator and multiplexing the signal with the other optical signal again by a coupler. CONSTITUTION:An optical amplifier 1 has a characteristic to obtain the gain of the optical signal having 1.53mum wavelength larger than the gain of the optical signal having 1.55mum wavelength and the output optical signal is outputted with an amplitude of the optical signal having 1.55mum wavelength smaller than the amplitude of the optical signal having 1.53mum wavelength. The output optical signal is branched into the optical signal of the 1.55mum wavelength and the optical signal of 1.53mum wavelength by a branching filter 8, the optical signal of 1.53mum wavelength is attenuated by an optical attenuator 10 and set at the same level as the optical signal of 1.55mum wavelength, and the optical signals of 1.55mum and 1.53mum wavelengths are multiplexed by a coupler 9 and outputted from an optical output terminal Tout.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplifier, and more particularly to an optical amplifier for amplifying wavelength-division multiplexed optical signals.

In recent years, an optical amplification repeater has been used in an optical communication system. The optical amplification repeater amplifies the optical signal attenuated in the optical fiber and transmits it again in the optical fiber.

In such an optical communication system, large capacity and long distance are required. For this purpose, wavelength multiplexing of optical signals is effective. On the other hand, the gain of the optical amplification device used in the optical amplification repeater differs depending on the wavelength. Therefore, when an optical signal is wavelength-multiplexed, the amplitude of the optical signal differs depending on the wavelength, which makes wavelength multiplexing difficult.

Therefore, such an optical amplifying device is required to have a structure capable of keeping the amplitude of the output optical signal constant regardless of the wavelength.

[0005]

2. Description of the Related Art FIG. 3 shows a block diagram of a conventional example.
In the figure, 1 indicates an optical amplifier. Optical amplifier 1 is driver 1
a, a pump laser 1b, and a multiplexer 1c. The driver 1a supplies a drive signal to the pump laser 1b. The pump laser 1b emits light according to the drive signal from the driver 1a. The output light of the pump laser 1b is supplied to the multiplexer 1c.

Laser light is supplied from the pump laser 1b to the multiplexer 1c and the main transmission optical signal is input, and the multiplexer 1c pumps the main transmission optical signal by the laser light from the pump laser 1b. , Amplifies the level of the main transmission optical signal.

The optical signal whose level has been amplified by the optical amplifier 1 is supplied to the monitoring circuit 3 via the erbume doped fiber 2.

The monitoring circuit 3 includes a coupler 3a, an APD (Avalanche Photo Diode) 3b serving as a light receiving element, a BPF (bandpass filter) 3c, a detection circuit 3d, and an SV (Supervis).
ory) circuit 3e. The coupler 3a takes out a part of the optical signal from the optical amplifier 1 and supplies it to the APD 3b.

The APD 3b receives the optical signal supplied from the coupler 3a and converts it into an electric signal. From the electric signal obtained by the APD 3b, the signal in the frequency band to be obtained by the BPF 3c is extracted and supplied to the detection circuit 3d. The detection circuit 3d detects a monitoring signal from the electric signal from the BPF 3c and supplies it to the SV control circuit 3e.

The SV control circuit 3e generates a control signal for controlling the gain of the optical amplifier 1 according to the supervisory signal and the supervisory information extracted from the optical signal and supplies it to the driver 1a of the optical amplifier 1.

The driver 1a controls the drive signal level supplied to the pump laser 1b according to the control signal from the SV control circuit 3e.

[0012]

However, since the conventional optical amplifying device has a different gain depending on the wavelength as shown in FIG. 4, when a plurality of optical signals are multiplexed and transmitted by wavelength multiplexing, the optical Each time the amplifier amplifies the level, a difference occurs in the output amplitude between the optical signals having different wavelengths, resulting in a difference in the characteristics such as S / N, and when one of the S / N signals is finally decoded. Since N is bad, there is a problem that equal characteristics cannot be obtained with a plurality of optical signals.

The present invention has been made in view of the above points, and an object of the present invention is to provide an optical amplifying device which can obtain a constant amplitude regardless of the wavelength.

[0014]

FIG. 1 shows a block diagram of the principle of the present invention. The optical amplification unit 4 amplifies a wavelength-division-multiplexed signal composed of a plurality of optical signals having different wavelengths with different gains depending on the wavelength.

The demultiplexing means 5 demultiplexes the plurality of optical signals amplified by the optical amplifying section 4 for each wavelength.

The optical attenuators 6-1 to 6-N attenuate the optical signals according to the gain of the optical amplifying section 4 for each of the optical signals demultiplexed by the demultiplexing means 5, and the optical signals are attenuated. Match the levels of.

The optical coupling means 7 includes the optical attenuators 6-1 to 6-1.
The plurality of optical signals extracted by 6-N are multiplexed again and output as a wavelength multiplexed signal.

[0018]

The wavelength-multiplexed signal amplified by the optical amplifier is demultiplexed by the demultiplexing means and output. The demultiplexed signal is compensated for the gain difference in the optical amplification section by the optical attenuator, and then multiplexed again by the optical coupling means to be a wavelength multiplexed signal. Therefore, the wavelength-multiplexed signal taken out from the optical coupling means does not have an amplitude difference for each wavelength due to the optical amplifier.

[0019]

FIG. 2 shows a block diagram of an embodiment of the present invention. In the figure, the same components as those of the block diagram of the conventional example of FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted.

In this embodiment, the input terminal Tin has a wavelength of 1.55 μm.
m and two optical signals of wavelength 1.53 μm are multiplexed and input. The multiplexed optical signal is level-amplified and output by the optical amplifier 1 serving as the optical amplifier 8.

The output optical signal of the optical amplifier 1 is supplied to the demultiplexer 8 which serves as the demultiplexing means 5. The demultiplexer 8 separates the supplied optical signal into an optical signal having a wavelength of 1.55 μm and an optical signal having a wavelength of 1.53 μm.

The optical signal having a wavelength of 1.55 μm is directly supplied to the coupler 9 serving as the optical coupling means 7, and the optical signal having a wavelength of 1.53 μm is supplied to the optical attenuator 1 corresponding to the optical attenuators 6-1 to 6-N.
It is supplied to the coupler 9 via 0.

The optical attenuator 10 attenuates the input optical signal level and outputs it. The attenuation of the optical attenuator 10 is set according to the gain difference between the gain of the optical amplifier 1 for the 1.55 μm wavelength optical signal and the gain of the 1.53 μm wavelength optical signal, and the 1.55 μm wavelength optical signal and the 1.53 μm wavelength optical signal are set. The level is set to be the same as that of the signal.

The coupler 9 combines the supplied optical signal of wavelength 1.55 μm and the supplied optical signal of wavelength 1.53 μm, multiplexes them, and outputs them.

Next, the operation of the apparatus will be described. Wavelength 1.55μ with its level set to almost the same at the optical input terminal Tin
An optical signal of m and an optical signal of wavelength 1.53 μm are multiplexed and input.

The optical signal input to the optical input terminal Tin is supplied to the optical amplifier 1 and level-amplified. The optical amplifier 1
It has a characteristic that the gain varies depending on the wavelength of the input optical signal.

The optical amplifier 1 has a characteristic that the gain of an optical signal having a wavelength of 1.53 μm is larger than the gain of an optical signal having a wavelength of 1.55 μm. Therefore, the output optical signal of the optical amplifier 1 has a wavelength of 1.55.
The amplitude of the optical signal of μm is smaller than that of the optical signal of wavelength 1.53 μm.

Next, the optical signal output from the optical amplifier 1 is demultiplexed by the demultiplexer 8 into an optical signal having a wavelength of 1.55 μm and an optical signal having a wavelength of 1.53 μm. After being demultiplexed, the optical signal with a wavelength of 1.53 μm is attenuated by the optical attenuator 10 and made equal to the level of the optical signal with a wavelength of 1.55 μm.
And the optical signal having a wavelength of 1.53 μm are multiplexed and output from the optical output terminal Tout.

Therefore, the optical signal output from the optical output terminal Tout has an optical signal level of 1.55 μm and an optical signal level of 1.53 μm.

Therefore, even in the case of wavelength multiplexing, a substantially constant level can be obtained regardless of the optical signal.
The characteristics such as S / N can be made equivalent.

When such an optical amplifier 1 is used in multiple stages, a post-demultiplexer, an optical attenuator, and a coupler are provided to pass all the optical amplifiers connected in multiple stages so that the optical signal amplitude for each wavelength is the same. Also as a configuration, a demultiplexer, an optical attenuator, and a coupler may be provided for each optical amplifier.

In the present embodiment, a case was considered in which an optical signal with a wavelength of 1.55 μm and an optical signal with a wavelength of 1.53 μm were multiplexed, but the present invention is not limited to this, and an optical signal with a plurality of wavelengths is not limited to this. The same compensation can be performed for the optical signal of each wavelength even in the case of multiplexing.

[0033]

As described above, according to the present invention, since the optical signal is attenuated by the optical attenuator, the gain difference due to the wavelength generated in the optical amplifying section can be compensated, so that a plurality of optical signals having different wavelengths are multiplexed. Even in the case of transmission, the optical signal level does not vary depending on the wavelength, and long-distance transmission is possible. Therefore, it has a feature that large capacity and long-distance optical communication can be performed.

[Brief description of drawings]

FIG. 1 is a principle block diagram of the present invention.

FIG. 2 is a block diagram of an embodiment of the present invention.

FIG. 3 is a block diagram of a conventional example.

FIG. 4 is a wavelength-gain characteristic diagram of an optical amplifier.

[Explanation of symbols]

4 Optical amplifier 5 demultiplexing means 6-1 to 6-N Optical attenuator 7 Optical coupling means

Claims (2)

[Claims] 1. An optical amplifier section (4) for amplifying a wavelength-division-multiplexed signal composed of a plurality of optical signals having different wavelengths with different gains according to wavelengths, and the plurality of optical amplifiers amplified by the optical amplifier section (4). Demultiplexing means (5) for demultiplexing the optical signal for each wavelength, and an optical signal according to the gain of the optical amplifying part (4) for each of the plurality of optical signals demultiplexed by the demultiplexing means (5). Attenuates,
An optical attenuator (6-1 to 6-N) for compensating relative gain differences depending on wavelengths of the plurality of optical signals; and a plurality of optical signals extracted from the optical attenuators (6-1 to 6-N). An optical amplifying device comprising: an optical coupling means (7) for re-multiplexing and outputting as a wavelength multiplexed signal. 2. The optical signal having the smallest amplitude at the time of output from the optical amplification section (4) among the plurality of optical signals is directly supplied to the optical coupling means (7), and the other optical signals have the same amplitude. The optical signal is supplied to the optical coupling means (7) through the optical attenuators (6-1 to 6-N) whose attenuation rates are set so as to be the same as the amplitude of the smallest optical signal. The optical amplification device according to claim 1.