JPH06140702A - Optical amplification star-coupler - Google Patents

Abstract

PURPOSE:To enable optical branching while performing optical amplification according to a small number of pumping light sources, concerning an optical amplification star-coupler having optical amplification function. CONSTITUTION:Photocouplers 12 having two inputs and many outputs are connected with the respective ports of a non-amplification optical star-coupler 11. Rare earth added optical fibers 13 are connected with the output ports of the photocouplers 12. The output ports are connected with the inputs of the photocouplers 12, and a single pumping light source 14 is connected with the input ports of the photocouplers 12. An optical switch 15 is installed which delivers the pumping lights inputted from the input ports to the output ports by turns, in the time division manner. The optical switch 15 is so constituted that the pumping light of the pumping light source 14 is supplied to each of the rare earth added optical fibers 13 before fluorescence radiated by the rare earth added optical fiber 13 becomes lower than a specified level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplification star coupler having an optical amplification function, and more particularly to an optical amplification star coupler for performing optical branching while performing optical amplification according to a small number of pumping light sources.

In the field of electronic circuits, an optical amplifier capable of directly amplifying light in the field of optical communication is indispensable for high functionality and high performance of an optical communication system, just as the amplifier is the basis of all device configurations. Is an element. An optical amplifier using a rare earth-doped optical fiber has Nd ³⁺ , Er ^{3+ in} the core of the fiber.
It is used as an optical amplification medium doped with rare earth elements such as Er.sup.3 ⁺ doped optical fiber has a laser transition frequency in the wavelength band of 1.55 μm, so optical amplification in this wavelength range is possible. Yes, it is expected to be applied to optical communication systems.

On the other hand, a 3 dB optical coupler (2-input / 2-output port configuration is adopted so that an optical signal input to the input port is 2
An optical star coupler, which is configured by connecting multiple optical output couplers for equal distribution output to one output port, has a function of performing optical branching processing between a plurality of input ports and output ports. Therefore, it is used in various places in optical communication systems. For example, in an optical frequency multiplex transmission system utilizing the potential broadband property of an optical fiber, as shown in FIG. 8, for bundling signals from light sources having a plurality of different oscillation wavelengths and sending them to one optical fiber. It is used as a multiplexer or a demultiplexer as shown in FIG. 9 for distributing a signal to each subscriber system. Further, the optical CATV system is expected to be used as a hub for distributing TV signals to each subscriber.

Since such an optical star coupler branches light, it naturally imposes attenuation of light. Therefore, when it is used in combination with an optical amplifier, the optical amplification property is increased. Need to have.

[0005]

2. Description of the Related Art Conventionally, in the case of performing optical branching using an optical star coupler, as disclosed in Japanese Patent Laid-Open No. 2-282226, an optical signal is sent by an optical fiber amplifier before the optical branching. A method of compensating for the loss due to branching by amplifying was adopted.

That is, as shown in FIG. 10, at the transmitting station side, an optical signal from the optical transmitter / receiver 1 such as 1.55 μm and a pumping light from the pumping light source 2 such as 1.49 μm are mixed by the optical multiplexer 3
Mix with. Then, in the optical fiber amplifier 4 such as Er ³⁺ doped optical fiber provided on the relay station side, the optical energy of the pumping light of 1.49 μm or the like is transited to the optical signal of 1.55 μm or the like to amplify the optical signal, The filter 5 removes the remaining pump light of 1.49 μm or the like, and then the optical star coupler 6 splits the optical signal into 1: n and distributes it to the n optical transceivers 7 of the receiving station. The method of going was adopted.

[0007]

However, according to such a conventional technique, there is a problem that the pump light sources 2 are required for the number of input ports of the optical star coupler 6. For example, when the optical star coupler 6 having 2 ^N inputs and 2 ^N outputs is used, 2 ^N pumping light sources 2 are required. Since an expensive semiconductor laser is used for the pumping light source 2, there is a problem that the optical communication system becomes extremely expensive if such a conventional technique is followed.

As one method for solving this,
As shown in FIG. 11, the pump light source 2 is connected to one of the input ports of the optical star coupler 6, and the optical fiber amplifier 4 such as Er ³⁺ -doped optical fiber is connected to each output port. So, with one excitation light source 2,
It is conceivable to adopt a configuration in which the optical signals input to the remaining input ports are amplified. That is, with the optical star coupler 6 configured as described above, an optical signal of 1.55 μm or the like and a pumping light of 1.49 μm or the like sent from the pumping light source 2 are mixed to form an optical fiber such as an Er ³⁺ doped optical fiber. With the amplifier 4, the light energy of the excitation light such as 1.49 μm is 1.55 μm.
The optical signal is amplified by making a transition to the optical signal such as m.

Certainly, if such a structure is adopted, the number of pumping light sources 2 can be reduced to one. However, according to such a configuration, since the pumping light emitted from the pumping light source 2 is also branched, a new problem arises in that the pumping light source 2 with high output is required.

The present invention has been made in view of the above circumstances, and provides a new optical amplification star coupler capable of performing optical branching while performing optical amplification in accordance with a small number of low-power pumping light sources. With the goal.

[0011]

FIG. 1 shows the principle configuration of the present invention. Reference numeral 10 is an optical amplification star coupler constructed according to the present invention.

This optical amplifying star coupler 10 is a non-amplifying non-amplifying optical star coupler 11 which has been widely used in the past.
And a plurality of two-input multi-output optical couplers 12 connected to, for example, output side ports of the non-amplifying optical star coupler 11.
A rare earth-doped optical fiber 13 connected to the output port of the optical coupler 12, a pumping light source 14 that emits pumping light,
The optical switch 15 outputs the pumping light emitted from the pumping light source 14 to the other input port of each optical coupler 12 in order in a time division manner.

Here, depending on the number of optical couplers 12,
There may be a plurality of pump light source 14 / optical switch 15 combinations.

[0014]

The rare-earth-doped optical fiber 13 emits fluorescence when the excitation light enters, and this fluorescence persists for several ms and then disappears, as shown in FIG.

Now, in the present invention, the optical switch 15
Supplies the pumping light emitted from the pumping light source 14 to each of the connected rare earth-doped optical fibers 13 via the optical coupler 12 before the fluorescence emitted from the rare-earth doped optical fiber 13 falls below a specified level. Adopt a configuration that goes on. from now on,
When the number of optical couplers 12 increases, a plurality of sets of excitation light sources 14 / optical switches 15 are provided in order to realize excitation light incidence before the extinction of fluorescence.

Upon receiving the supply of pumping light from the pumping light source 14 via the optical switch 15, the optical coupler 12 outputs the amplification target optical signal transferred from the non-amplifying optical star coupler 11 and the pumping light source 14. The excitation light is mixed and sent to the rare earth-doped optical fiber 13, and the rare earth-doped optical fiber 1
When the mixed light is received, 3 amplifies the optical signal by shifting the optical energy of the excitation light to an optical signal while the fluorescence continues.

As described above, according to the present invention, the optical signal to be branched by the non-amplifying optical star coupler 11 can be amplified by preparing only a small number of pumping light sources 14 of low output. It will be possible.

[0018]

EXAMPLES The present invention will be described in detail below with reference to examples. FIG. 3 shows an embodiment of an optical amplification star coupler 10 having 2 ^N-1 inputs and 2 ^N outputs constructed according to the present invention.

In the figure, 11a is a non-amplifying optical star coupler having no amplification function for 2 ^N-1 inputs and 2 ^N-1 outputs, and 12a-i (i
= 1 to 2 ^N-1 ) is a 3 dB optical coupler connected to the output port of the unamplified optical star coupler 11a, 13a is an Er ³⁺ doped optical fiber connected to the output port of the 3 dB optical coupler 12a-i, and 14a is A semiconductor laser that emits pumping light of 1.49 μm, 15a is an optical switch that outputs the pumping light emitted by the semiconductor laser 14a to the other input port of each 3 dB optical coupler 12a-i in a time-division order, and 16 is a semiconductor. An isolator for processing the pumping light output from the laser 14a so as not to return to the semiconductor laser 14a, and a switch driver 17 for controlling the switching of the optical switch 15a.

FIG. 4 illustrates an optical circuit configuration of the optical switch 15a. The optical switch 15a is a 2-input 2-output that selectively outputs an optical signal input to an input port to either one of two output ports according to a voltage applied to an electrode, as shown in FIG. Optical switch (2:
(2 optical switch) is used as a basic constituent element, and as shown in FIG. 4, an (N-1) stage connection of a 2: 2 optical switch that receives an optical signal output from the preceding 2: 2 optical switch as an input. Composed of. According to this configuration, the optical switch 15a
Depending on the voltage mode applied by the switch driver 17, any one of the input ports ((1) to ((1) to () in FIG. 3) of the 3 dB optical coupler 12a-i provided with 2 ^N-1 pumping light output from the semiconductor laser 14a. 2 ^N-1 )) will be output in order by time division.

The fluorescence characteristics of the rare earth-doped optical fiber 13 are shown in FIG. 2. In the Er ³⁺ -doped optical fiber 13a, the fluorescence time constant is about several ms. Therefore, if the fluorescence emitted from the Er ³⁺ -doped optical fiber 13a is allowed to decrease to 0.1 dB, several to several tens of μS after the excitation light is cut off.
During the period, it is not necessary to supply the pumping light to the Er ³⁺ -doped optical fiber 13a. That is, since it is sufficient to supply the excitation light to the Er ³⁺ -doped optical fiber 13a at a cycle of several to several tens of μS, for example, when the excitation light drive pulse width is 1 μS and the cycle is 1 mS, 3 dB Optical coupler 12
If the number of a-i is about "2048", the optical switch 15a
By this operation, as shown in FIG. 6, the fluorescence emitted from each Er ³⁺ -doped optical fiber 13a can be suppressed by a decrease of 0.1 dB.

Thus, according to the present invention, the optical switch
15a is Er according to the time division processing.³⁺Doped optical fiber
Before the fluorescence emitted by 13a falls below the specified value, the semiconductor
The pumping light output from the body laser 14a is converted into the 3 dB optical coupler 12
Each Er of connection destination via a-i ³⁺In the doped optical fiber 13a
It is configured to supply to the customer.

When the 3 dB optical coupler 12a-i receives the supply of the pumping light from the semiconductor laser 14a via the optical switch 15a, the 1.55 μm optical signal to be amplified transferred from the unamplified optical star coupler 11a. And 1.49 μm excitation light output from the semiconductor laser 14a are mixed to obtain E
sent to r ³⁺ doped optical fiber 13a, Er ³⁺ doped optical fiber 13a receives the mixed light, while the fluorescence persists, 1.55 .mu.m light energy of the excitation light 1.49μm In this configuration, the optical signal is amplified by making a transition to the optical signal.

In this way, the unamplified optical star coupler 1
If the number of output ports of 1a is, for example, about “2048”, the optical amplification star coupler 10 amplifies the optical signal input to the input port of the unamplified optical star coupler 11a with one semiconductor laser 14a. While branching.

FIG. 7 shows an embodiment of the optical amplification star coupler 10 of 2 ^N input and 2 ^N output constructed according to the present invention. In the figure, the same components as those described in the embodiment of FIG. 3 are designated by the same symbols.

In the optical amplification star coupler 10 with 2 ^N-1 inputs and 2 ^N outputs shown in FIG. 3, the 3 dB optical coupler 1 is provided only at the output port of the non-amplification optical star coupler 11a with 2 ^N-1 inputs and 2 ^N- 1.
In contrast to the configuration in which 2a is connected, this FIG.
2 ^N input and 2 ^N output optical amplifier star coupler 10 of the embodiment
Then, 2 ^N-1 input 2 ^N-1 non-amplifying optical star coupler 11a
The 3 dB optical coupler 12a is connected to the input / output port of the semiconductor laser 14a, the optical switch 15a, the isolator 16 and the switch driver 1 on the input port side and the output port side, respectively.
By providing 7, an optical amplification star coupler with 2 ^N inputs and 2 ^N outputs is realized.

[0027]

As described above, according to the present invention,
An optical amplifier star coupler capable of amplifying an optical signal to be branched can be realized by preparing a small number of pumping light sources with low output.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram of fluorescence characteristics of a rare earth-doped optical fiber.

FIG. 3 is an example of the present invention.

FIG. 4 is an optical circuit configuration diagram of an optical switch.

FIG. 5 is an optical circuit configuration diagram of a 2: 2 optical switch.

FIG. 6 is a time chart of pumping light supply.

FIG. 7 is another embodiment of the present invention.

FIG. 8 is an explanatory diagram of a technique of using an optical star coupler.

FIG. 9 is an explanatory diagram of a technique of using the optical star coupler.

FIG. 10 is an explanatory diagram of a conventional technique.

FIG. 11 is a configuration example for solving the conventional technique.

[Explanation of symbols]

 10 Optically Amplified Star Coupler 11 Non-Amplified Optical Star Coupler 12 Optical Coupler 13 Rare Earth Doped Optical Fiber 14 Pumping Light Source 15 Optical Switch

Claims (1)

[Claims] 1. An optical amplification star coupler having an optical amplification function, which corresponds to both the input side port and the output side port of the optical star coupler (11) having no optical amplification function, or to correspond to either one of the ports. In addition, a configuration is adopted in which a 2-input multi-output optical coupler (12) is connected, and a configuration in which a rare earth-doped optical fiber (13) is connected to the output port of the optical coupler (12), and the optical coupler ( Optical star coupler (11) above
The output port is connected to the input port that is not connected to the input port, and a single pumping light source (14) is connected to the input port, and the pumping light input from the input port is output in a time division manner. Equipped with one or more optical switches (15) that operate to sequentially output to the mouth, in the optical switch (15), fluorescence emitted from the rare earth-doped optical fiber (13) is lower than a specified level. Excitation light source before
An optical amplification star coupler characterized in that it is configured to supply the pumping light emitted from (14) to each of the rare earth-doped optical fibers (13) at the connection destination.