JP2001148527A - Optical amplifier and gain controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily adjust the aging of the transmission characteristics of an optical transmission line. SOLUTION: Signal light S1 being inputted into an input port 10 passes through a WDM photocoupler 16 for inputting into an optical amplification fiber 12, and excitation light being outputted from an excitation light source 14 is inputted into the optical amplifying fiber 12 by the WDM photocoupler 16. The optical amplification fiber 12 outputs signal light that has been optical amplified, and the excitation light that is not been absorbed toward an WDM coupler 18. The signal light that is outputted from the optical amplifying fiber 12 and is optically amplified is transmitted through the WDM photocoupler 18 and an optical isolator 24 for outputting to he outside from an optical output port 26. An excitation light, constituent that is not absorbed by the optical amplification fiber 12, branches from the main line family by the WDM photocoupler 18 for entering a photo/heat exchanger 22 via a variable attenuator 20. The photo/heat exchanger 22 generates heat corresponding to the quantity of incident light. The generated heat is applied to the optical amplification fiber 12 to heat it. According to the amount of attenuation of the variable attenuator 20, heating from the optical/heat exchanger 22 to the optical amplification fiber 12 is adjusted.

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 a gain adjuster, and more particularly, to an optical amplifier using a rare earth-doped medium as an optical amplifying medium for optical communication and a gain for adjusting the wavelength dependence of the gain. Regarding the regulator.

[0002]

2. Description of the Related Art In an optical amplification repeater transmission line, the wavelength dependence of the gain in the optical amplification repeater transmission line changes due to deterioration with time of an optical fiber and breakage repair of an optical fiber cable. Currently, as a means for compensating for this change, an active gain equalizer using a Faraday rotator has been proposed (T. Naito et al., "Active G").
ain Slope Compensation in
Large-Capacity, Long-Hau
l WDM Transmission System
m ", 10th Optical Amplifier
s and Their Applications
Technical Digest 36-39 / WC
−5-1, June 9-11, 1999, Na
ra, Japan).

[0003]

However, in the conventional example, it is necessary to arrange a plurality of individual optical elements on the optical axis, so that not only the production is troublesome, but also it is difficult to reduce the size.

An object of the present invention is to provide an optical amplifying apparatus and a gain adjuster which can be reduced in size and can easily adjust the wavelength dependence of gain.

[0005]

An optical amplifier according to the present invention is an optical amplification medium, an excitation light source for generating excitation light for exciting the optical amplification medium, and a heating means for heating the optical amplification medium. And a heating means capable of adjusting the amount of heat applied to the optical amplification medium.

The wavelength characteristic of the gain of the optical amplification medium can be adjusted by adjusting the amount of heat applied by the heating means to the optical amplification medium. Therefore, even if the transmission characteristic of the optical transmission line changes, it can be easily adjusted.

[0007] Preferably, the heating means is a light extracting means for extracting the excitation light component not absorbed by the light amplifying medium, and a light / heat converting means for converting the light extracted by the light extracting means into heat. Consists of As a result, the pump light not consumed by the optical amplification medium can be effectively used. By disposing a variable attenuator between the light extracting means and the light / heat converting means and adjusting the amount of attenuation, the amount of heating of the optical amplification medium can be easily adjusted.

[0008] Even when the distance between the light / heat converting means and the optical amplifying medium is changed, the heating amount of the optical amplifying medium can be adjusted.

The optical amplifier according to the present invention also includes an optical amplification medium, an excitation light source for generating excitation light for exciting the optical amplification medium, and the generation of the excitation light source from one of the optical amplification media to the optical amplification medium. A first optical coupler for introducing the excitation light to be excited, a second optical coupler for extracting the excitation light component output from the other of the optical amplification medium, and the light extracted by the second optical coupler as heat. And a light / heat converting means for converting the heat and applying the generated heat to the optical amplification medium.

By adjusting the amount of heat applied to the optical amplifying medium by the light / heat converting means, it is possible to adjust the wavelength characteristic of the gain of the optical amplifying medium. Can be modified. In addition, the excitation light not consumed by the optical amplification medium can be effectively used.

By disposing a variable attenuator between the light extracting means and the light / heat converting means and adjusting the amount of attenuation, the heating amount of the optical amplification medium can be easily adjusted.

[0012] Even if the distance between the light / heat conversion means and the optical amplifying medium is changed, the heating amount of the optical amplifying medium can be adjusted.

A gain adjuster according to the present invention is a device for adjusting the gain of an optical amplifier, comprising: a light extracting means for extracting, from a signal transmission path, an excitation light component transmitted through an optical amplification medium of the optical amplifier; And a light / heat converting means for converting the light extracted by the light extracting means into heat and applying the generated heat to the optical amplifying medium.

The wavelength characteristic of the gain of the optical amplifying medium can be adjusted by adjusting the amount of heat applied to the optical amplifying medium by the light / heat converting means, so that even if the transmission characteristic of the optical transmission line changes, it can be easily adjusted. Can be modified. In addition, the excitation light not consumed by the optical amplification medium can be effectively used.

By disposing a variable attenuator between the light extracting means and the light / heat converting means and adjusting the amount of attenuation, the heating amount of the optical amplification medium can be easily adjusted.

Even if the distance between the light / heat converting means and the optical amplifying medium is changed, the amount of heating of the optical amplifying medium can be adjusted.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic block diagram of an embodiment of the present invention. Reference numeral 10 denotes an input port for inputting the signal light S1 to be optically amplified, 12 denotes an optical amplification fiber doped with erbium, 14 denotes an excitation light (980 nm band or 1480 nm) for exciting erbium added to the optical amplification fiber 12.
A pump light source 16 for generating a band), a wavelength division multiplexing light (WDM) coupler for multiplexing the pump light output from the pump light source 14 with the signal light S1 from the input port 10 and supplying the multiplexed light to the optical amplification fiber 12. , 18 are WDM optical couplers that pass through the optical amplifying fiber 12 and split the remaining pump light absorbed by the optical amplifying fiber 12, and 20 attenuates a desired amount of the pump light component split by the optical coupler 20. A variable attenuator 22 whose attenuation can be adjusted, a light / heat converter 22 that converts light from the variable attenuator 20 into heat and supplies the heat to the optical amplification fiber 12, and a return light 24 from the downstream side. Is an optical isolator for preventing the light from entering the optical amplification fiber 12, and 26 is an output port for outputting the optically amplified signal light S1.

The operation of this embodiment will be described. Input port 1
The signal light S1 input to 0 passes through the WDM optical coupler 16 and is input to the optical amplification fiber 12. On the other hand, the pump light output from the pump light source 14 is input to the optical amplification fiber 12 by the WDM optical coupler 16. Optical amplification fiber 1
The erbium 2 absorbs the input pump light and is pumped to amplify the signal light S1. The optical amplification fiber 12
Usually, it absorbs about several tens of percent of the input pump light and outputs the rest. That is, the optical amplification fiber 12 outputs the optically amplified signal light and the pump light that has not been completely absorbed to the WDM coupler 18.

The optically amplified signal light output from the optical amplification fiber 12 passes through the WDM optical coupler 18 and the optical isolator 24, and is output from the optical output port 26 to the outside.

On the other hand, the pump light component not absorbed by the optical amplification fiber 12 is branched off from the main line by the WDM optical coupler 18 and enters the optical / heat converter 22 via the variable attenuator 20. The light / heat converter 22 generates heat according to the amount of incident light. The generated heat is applied to the optical amplification fiber 12, and heats the optical amplification fiber 12.

In the erbium-doped optical amplification fiber 12, the wavelength dependence of the gain generally changes depending on the temperature. Specifically, when the optical amplification fiber 12 is warmed, the gain on the long wavelength side increases and the gain on the short wavelength side decreases. On the other hand, the wavelength dependence of the gain (loss) of the optical transmission line changes due to the deterioration of the optical fiber loss with time and the repair of the optical fiber cable by breaking. The side gain tends to decrease. Therefore, the amount of heating of the optical amplification fiber 12 may be reduced in response to a change in transmission characteristics due to a change over time or the like. In order to adjust the amount of heating of the optical amplification fiber 12, there are a method of increasing the attenuation of the variable attenuator 20 and a method of mechanically or thermally separating the light / heat converter 22 from the optical amplification fiber 12. Either method may be used, or both may be used in combination.

In this way, it is possible to easily compensate for the change in the wavelength dependence of the gain (loss) of the optical transmission line due to the deterioration with time of the optical fiber loss and the repair of the optical fiber cable by interrupting and the like.

In the embodiment shown in FIG.
2 was excited from the front, but it is clear that the same is true when excited from the rear.

In the embodiment shown in FIG. 1, the optical amplification fiber 12 is heated by using the pump light which has not been consumed. However, even if an electric heater is used, the wavelength dependence of the gain of the optical amplification fiber is similarly obtained. Can be adjusted. The electric heater can be replaced by an electric / electronic device in an optical repeater. For example, the temperature distribution in the optical repeater is not uniform, and the temperature is high near an element or a circuit that consumes a large amount of power, and the temperature is low in a portion where passive components are gathered. Therefore, the same effect can be obtained by moving the optical amplification fiber to a position having a different temperature in the optical repeater.

[0026]

As can be easily understood from the above description, according to the present invention, the wavelength dependence of the gain of an optical transmission line can be adjusted with a simple configuration. Thereby, the optical transmission system can be stably operated for a long time.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of the present invention.

[Description of Signs] 10: Input port 12: Optical amplification fiber 14: Pump light source 16: Wavelength division multiplexing (WDM) optical coupler 18: WDM optical coupler 20: Variable attenuator 22: Optical / heat converter 24: Optical isolator 26 : Output port

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masakazu Nakata F-term (reference) 5-3 2-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Keididi Submarine Cable System Co., Ltd.

Claims (10)

[Claims] 1. An optical amplifying medium, an excitation light source for generating excitation light for exciting the optical amplifying medium, and heating means for heating the optical amplifying medium, wherein the amount of heat applied to the optical amplifying medium is adjustable. An optical amplifier comprising a heating means. 2. The light extracting means for extracting the excitation light component not absorbed by the optical amplification medium, wherein the heating means comprises:
Light for converting the light extracted by the light extraction means into heat /
2. The optical amplifier according to claim 1, comprising a heat conversion means. 3. The optical amplifier according to claim 2, further comprising a variable attenuator disposed between said light extraction means and said light / heat conversion means. 4. The optical amplifier according to claim 2, wherein a distance between said light / heat converting means and said optical amplification medium can be changed. 5. An optical amplification medium, an excitation light source for generating excitation light for exciting the optical amplification medium, and a pump light source for introducing the excitation light generated by the excitation light source from one of the optical amplification media to the optical amplification medium. 1, an optical coupler, a second optical coupler for extracting an excitation light component output from the other of the optical amplifying medium, and light converted by the second optical coupler into heat, and the generated heat is converted to heat. An optical amplifier, comprising: a light / heat converting means for applying a light to an optical amplifying medium. 6. The optical amplifier according to claim 5, further comprising a variable attenuator disposed between said light extraction means and said light / heat conversion means. 7. The optical amplifier according to claim 5, wherein a distance between the light / heat conversion means and the optical amplification medium can be changed. 8. An apparatus for adjusting the gain of an optical amplifier, comprising: a light extraction unit that extracts a pump light component transmitted through an optical amplification medium of the optical amplifier from a signal transmission path; A light / heat converting means for converting the generated light into heat and applying the generated heat to the optical amplifying medium. 9. The gain adjuster according to claim 8, further comprising a variable attenuator disposed between said light extraction means and said light / heat conversion means. 10. The gain adjuster according to claim 8, wherein a distance between said light / heat converting means and said optical amplification medium can be freely changed.