JP2003078193A - Light amplifier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light amplifier suitable for miniaturization. SOLUTION: This light amplifier is constituted of n (which is an integer larger than 1) pieces of dope fibers whose rare-earth elements are respectively doped, n pieces of input side optical fibers which are respectively optically connected to the input edges of those n pieces of dope fibers, n pieces of output side optical fibers which are respectively optically connected to the output edges of the n pieces of dope fibers, a light source collimeter which radiates a pump light, and a fiber member arranged in the radiation region of the light source collimeter between the input edge of the dope fiber and the input side fiber for penetrating an optical signal to be amplified, and for reflecting the pump light in order to make it incident to each dope fiber.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical amplifier,
More specifically, the present invention relates to an optical amplifier capable of amplifying optical signals of a plurality of channels and suitable for downsizing.

[0002]

2. Description of the Related Art In recent years, low loss (for example, 0.2 dB / k)
The technique for producing and using the silica-based optical fiber described in m) has been established, and an optical communication system using the optical fiber as a transmission line has been put to practical use. Further, an optical amplifier that amplifies an optical signal (or signal light) has been put to practical use in order to compensate for loss due to an optical fiber and enable long-distance transmission.

It is known in the prior art that an optical amplification medium to which a signal light to be amplified is supplied and a pumping optical amplification medium so that the optical amplification medium provides a gain band including the wavelength of the signal light ( Pumping means).

For example, an erbium-doped fiber amplifier (EDFA) has been developed in order to amplify a signal light in a wavelength band of 1.55 μm, which has the smallest loss in a silica fiber. The EDFA includes an erbium-doped fiber (EDF) as an optical amplification medium, and a pump light source for supplying pump light having a predetermined wavelength to the EDF. For example, a gain band including a wavelength of 1.55 μm can be obtained by using pump light having a wavelength of 0.98 μm band or 1.48 μm band.

On the other hand, there is wavelength division multiplexing (WDM) as a technique for increasing the transmission capacity of an optical fiber. In a system to which WDM is applied, a plurality of optical carriers having different wavelengths are used. A plurality of optical signals obtained by independently modulating each optical carrier are wavelength division multiplexed by an optical multiplexer, and the WDM signal light obtained as a result is sent out to an optical fiber transmission line. At the receiving end, the received WDM signal light is separated into individual optical signals by the optical demultiplexer, and the transmission data is reproduced based on each optical signal.

When a system is constructed by combining WDM and an optical amplifier, the transmission distance is limited by the wavelength characteristic of the gain of the optical amplifier represented by the gain deviation or the gain slope. For example, in a typical EDFA, wavelength 1.
Gain deviation occurs near 55 μm. When gain deviations are accumulated for a plurality of cascade-connected EDFAs, the optical SNR (signal-to-noise ratio) of channels included in a band having a small gain deteriorates. Therefore, in order to enable high quality transmission, it is desirable that the wavelength characteristic of the gain of the optical amplifier is flat.

[0007]

As described above, although the basic structure of the optical amplifier is simple, various additional functions are required when it is used by incorporating it into an actual system. For example, ALC (automatic level control) is adopted in order to keep the output power level constant regardless of the fluctuation of the input power level, which widens the input dynamic range. Further, the gain is controlled to be constant in order to keep the wavelength characteristic of the gain constant.

In order to obtain such an additional function, an optical coupler for monitoring, a photodetector and other parts are often used. As a result, the number of parts tends to increase,
It was difficult to downsize the optical amplifier.

As a related technique for downsizing an optical amplifier, there is one described in Japanese Patent Laid-Open No. 8-304855.

Therefore, an object of the present invention is to provide an optical amplifier suitable for miniaturization.

Other objects of the invention will be apparent from the following description.

[0012]

According to an aspect of the invention,
N (n is an integer greater than 1) doped fibers each doped with a rare earth element, n input-side optical fibers optically connected to input ends of the n doped fibers, and n N output-side optical fibers optically connected to the output ends of the two doped fibers, a light source collimator for emitting pump light, an emission region of the light source collimator, and an input end of the doped fiber and the input There is provided an optical amplifier provided with a filter member which is provided between the side fibers and transmits an optical signal to be amplified and reflects the pump light to enter each doped fiber.

According to another aspect of the present invention, n (n is an integer greater than 1) doped fibers each doped with a rare earth element, and optically connected to the input ends of the n doped fibers, respectively. N input side optical fibers,
N output side optical fibers respectively optically connected to the output ends of the n doped fibers, a light source collimator for emitting pump light, an emission region of the light source collimator and an output end of the doped fiber An optical amplifier is provided, which is provided between the output side fiber and a filter member that transmits the amplified optical signal and reflects the pump light to enter each doped fiber.

In the optical amplifier according to the present invention, the light source collimator for emitting pump light and the filter member are arranged in a specific positional relationship, so that efficient parts arrangement and the like are possible, and the optical amplifier can be miniaturized. It will be possible.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a partially cutaway plan view showing an embodiment of an optical amplifier according to the present invention. In addition, FIG.
FIG. 2B is a diagram of the optical amplifier shown in FIG. 2A, taken along line 2A-2A, and FIG. 2B is a diagram similarly seen along line 2B-2B.

This optical amplifier includes a 4-port optical fiber array 2 as an input port, a lens array 4, a polarization-independent optical isolator 6, and a pump along a propagation path of an optical signal to be amplified. A filter member 8 provided in relation to light, a lens array 10, an EDF (erbium-doped fiber) module 12, a lens array 13, a polarization-independent optical isolator 14, a lens array 16, and a branching coupler array 18. And a 4-port optical fiber array 20 as an output port in this order. Further, a 4-port PD (photodetector or photodiode) array 22 is provided in association with the branch coupler array 18, and each component is mounted on a substrate 23.

The optical fiber array 2 is constituted by supporting four optical fibers 24 (# 1 to # 4) in parallel with each other, and these fibers have a single optical signal or a plurality of optical signals to be amplified. WDM signal light obtained by wavelength division multiplexing optical signals is supplied. When WDM signal light is supplied to each of the optical fibers 24 (# 1 to # 4), they may have spectra in the same band or may have spectra in different bands. good.

The lens array 4 includes an optical fiber 24 (# 1
~ # 4) four lenses 2 provided to face the output end
Have six. Due to the condensing action of each lens 26, the signal light emitted from the output end of each fiber is generally collimated and shaped into a parallel beam.

The optical isolator 6 and the filter member 8 are
It is provided so that the parallel beam collimated by the lens 26 passes through. The filter member 8 includes a transparent plate 28 that is obliquely arranged with respect to each beam, and four filter films 30 (# 1 to # 4) provided at the beam passage position of the plate 28.

The lens array 10 includes a filter film 30 (#
It is provided with four lenses 32 for converging the beams transmitted through 1 to # 4).

The EDF module 12 includes four EDFs 3
6 (# 1 to # 4) is wound around the bobbin 38. The light beams focused by the lens 32 are supplied to the input ends of the EDFs 36 (# 1 to # 4), respectively.

The lens array 13 is an EDF 36 (# 1).
It has four lenses 30 provided so as to face the output end on the side opposite to the input end of the. EDF3
The light emitted from the output terminals 6 (# 1 to # 4) is collimated by the lens 40, passes through the optical isolator 14, and the four lenses 42 of the lens array 16 are transmitted.
Be focused by. And the focused light is
The branching coupler array 18 separates the main signal light and the monitor light, and the main signal light is composed of four optical fibers 44 constituting an optical fiber array 20 as an output port.
The monitor light supplied to (# 1 to # 4) is supplied to the PD array 22.
Of each PD. The power distribution ratio of the main signal light and the monitor light is, for example, 10: 1.

Through the filter member 8, the EDF 36 (# 1
A light source collimator 46 is provided to supply pump light to each of # 4 to # 4. The light source collimator 46 is
The sleeve 5 includes an optical fiber 48 optically connected to the pump light source, and a lens 50 for converting the beam parameter of the pump light emitted from the output end of the optical fiber 48.
2 is configured to be held in a predetermined positional relationship.

The pump light whose beam parameters have been converted is reflected by each of the filter films 30 (# 1 to # 4), and passes through the plate 28 together with the signal light to be amplified,
Each of the DFs 36 (# 1 to # 4) is supplied from its input end.

Referring to FIG. 3, there is shown an example of wavelength characteristics of the transmittance of the filter film 30 (# 1 to # 4) shown in FIG. In the filter films 30 (# 1 to # 4), the transmittance is smaller than 0.2% only in a certain band centered on the center wavelengths λ _{p1 to} λ _p4, and is larger than 98% in the other bands. It is like this. Wavelength λ _p1
To [lambda] _p4 is in the range of, for example, 1.46 to 1.48 .mu.m, which does not overlap so that the signal wavelength band (for example, 1.
53 to 1.61 μm) is set. Therefore, the pump light is reflected by the filter films 30 (# 1 to # 4), and the signal light to be amplified is transmitted through the filter films 30 (# 1 to # 4).

The pump light source to which the optical fiber 48 of the light source collimator 46 is optically connected may be a single light source having a spectrum including the entire pump light band shown in FIG. 3, or a plurality of light sources. It may be a light source that is obtained by combining the pump light from the. For this multiplexing, for example, wavelength division multiplexing by an optical multiplexer or polarization combination can be used.

In this embodiment, since a plurality of filter films 30 (# 1 to # 4) having different wavelength characteristics of transmittance are used, when a plurality of light sources are used as pump light sources, the EDF 36 (# The gain control of 1 to # 4) can be easily performed independently. Also, EDF3
When pump lights of different wavelengths are required, such as when the bands of the signal lights to be amplified to be supplied to 6 (# 1 to # 4) are different, this can be easily dealt with.

FIG. 4 is a partially cutaway plan view showing a second embodiment of the optical amplifier according to the present invention. 5A is a view of the optical amplifier shown in FIG. 4 taken along line 5A-5A, and FIG. 5B is a view of the same taken along line 5B-5B.

This embodiment is characterized in that it is a backward pumping optical amplifier, whereas the embodiment shown in FIG. 1 is a forward pumping optical amplifier. That is, in the embodiment shown in FIG. 1, the filter member 8 is provided between the optical isolator 6 and the lens array 10 so that the pump light from the light source collimator 46 is in the same direction as the signal light to be amplified.
36 (# 1 to # 4), the filter member 8 is provided between the lens array 13 and the optical isolator 14 in the embodiment shown in FIG. The pump light from the light source collimator 46 is EDF3.
The output terminals 6 (# 1 to # 4) are supplied to the EDFs.

Further, in this embodiment, a branch coupler array 54 is provided between the output end of the optical fiber array 2 and the lens array 4 in order to monitor the power of each signal light at the input port, and the PD array is attached thereto. 56
Is provided.

As a result, the PD array 56 can monitor the input power of the signal light and the PD array 22 can monitor the output power of the signal light.
The gain of this optical amplifier can be easily known from the monitoring values of both. For example, by controlling the pump light power based on the obtained gain, the gain can be made constant or the wavelength characteristic of the gain can be made constant.

FIG. 6 is a side view showing a third embodiment of the optical amplifier according to the present invention. Compared with the embodiment shown in FIG. 4, this embodiment is characterized in that it facilitates mounting of each component on the board 23 by using the board 23 having a predetermined shape. That is, with respect to the lens arrays 4 and 10, the optical isolator 6, the filter member 8, the branch coupler array 54, etc., the packing 58 is formed on the substrate 23 to facilitate their positioning, and the fiber arrays 2 and 36. about,
By providing the V-grooves on the substrate 60, their alignment is facilitated.

When silicon is used as the material of the substrate 23, the V groove 60 can be easily formed by anisotropic etching or the like. A substrate made of glass may be used as the substrate 23.

In the embodiment described above, the EDF is used as the doped fiber. In this case, the pump light band is, for example, 1460 to 1480 mm, and the signal light band is 1500 to 1620 mm.

The present invention is also applicable to doped fibers doped with other rare earth ions. For example, by adopting Nd and setting the pump light band to 800 to 830 nm, the signal light band is set to 1320 to 1400.
can be nm. Further, by using Tm and setting the pumping light band to 1380 to 1410 nm, the signal light band can be set to 1450 to 1500. Further, by setting the pumping light band to 980 to 1050 nm using Pr, the signal light band can be set to 1280 to 1340 nm. Alternatively, Yb is used to set the pumping light band to 910 to 980n.
By setting m, the band of the signal light can be set to 970 to 1120 nm.

According to the embodiment described above, extra processing such as EDF in the optical amplifier is unnecessary, and since various parts are arrayed, the optical amplifier can be downsized. In particular, by processing the substrate 23 into a predetermined shape as in the embodiment shown in FIG. 6, each component can be easily mounted and an optical amplifier that can be easily manufactured can be provided. .

The present invention includes the following supplementary notes.

(Supplementary Note 1) n (n is an integer larger than 1) doped fibers each doped with a rare earth element,
N input-side optical fibers optically connected to the input ends of the n-doped fibers, and n output-side optical fibers optically connected to the output ends of the n-doped fibers And a light source collimator that emits pump light, and a light source collimator that is provided in the radiation region and between the input end of the doped fiber and the input side fiber, transmits the optical signal to be amplified, and transmits the pump light. An optical amplifier comprising: a filter member that reflects the light and makes it incident on each doped fiber.

(Supplementary Note 2) n (n is an integer greater than 1) doped fibers each doped with a rare earth element,
N input-side optical fibers optically connected to the input ends of the n-doped fibers, and n output-side optical fibers optically connected to the output ends of the n-doped fibers And a light source collimator that emits pump light, and a radiation region of the light source collimator that is provided between the output end of the doped fiber and the output-side fiber, transmits the amplified optical signal, and transmits the pump light. An optical amplifier comprising: a filter member that reflects the light and makes it incident on each doped fiber.

(Supplementary Note 3) In the optical amplifier according to Supplementary Note 1 or 2, the filter member is provided at a plate transparent to an optical signal to be amplified and at a position where the optical signal is transmitted. An optical amplifier including a plurality of filter films.

(Supplementary Note 4) The optical amplifier according to Supplementary Note 3, wherein the plurality of filter films have different wavelength characteristics of transmittance.

(Supplementary Note 5) The optical amplifier according to Supplementary Note 1 or 2, wherein the light source collimator is an optical fiber optically connected to a pump light source, and a beam parameter of the pump light emitted from the optical fiber. And a lens that converts the beam parameters, and the pump light having the converted beam parameters is applied to the filter member.

[0044]

As described above, according to the present invention,
There is an effect that an optical amplifier suitable for miniaturization can be provided. Since the effects obtained by the specific embodiment of the present invention are as described above, the description thereof will be omitted.

[Brief description of drawings]

FIG. 1 is a partially cutaway plan view showing a first embodiment of an optical amplifier according to the present invention.

2A and 2B are views of the optical amplifier shown in FIG. 1 taken along lines 2A-2A and 2B-2B, respectively.

FIG. 3 is a graph showing characteristics of a filter member.

FIG. 4 is a partially cutaway plan view showing a second embodiment of the optical amplifier according to the present invention.

5A and 5B are views of the optical amplifier shown in FIG. 4 taken along lines 5A-5A and 5B-5B, respectively.

FIG. 6 is a side view showing a third embodiment of the optical amplifier according to the present invention.

[Explanation of symbols]

2,20 fiber array 4,10,13,16 lens array 8 Filter member 12 EDF module 46 light source collimator

Claims (2)

[Claims] 1. N-doped fibers (n is an integer greater than 1) each doped with a rare earth element, and n input-side lights optically connected to the input ends of the n-doped fibers, respectively. A fiber, n output optical fibers optically connected to the output ends of the n doped fibers, a light source collimator for radiating pump light, and a radiation region of the light source collimator and for the doped fiber An optical amplifier, comprising: a filter member provided between an input end and the input-side fiber, which transmits an optical signal to be amplified and reflects the pump light to enter each doped fiber. 2. N (n is an integer greater than 1) doped fibers each doped with a rare earth element, and n input-side lights optically connected to the input ends of the n doped fibers, respectively. A fiber, n output optical fibers optically connected to the output ends of the n doped fibers, a light source collimator for radiating pump light, and a radiation region of the light source collimator and for the doped fiber An optical amplifier comprising: a filter member which is provided between an output end and the output side fiber, transmits an amplified optical signal, reflects the pump light, and causes the pump light to enter each doped fiber.