JPH02282229A - Optical wavelength selecting circuit - Google Patents

Abstract

PURPOSE:To allow the selective passage of the light signal of a required wavelength from a wavelength multiplex light signal without depending on polarization by making the light signal subjected to a wavelength sepn. In a wavelength separating circuit to plural rare earth element-added optical fiber amplifier circuits, then guiding the light signal to an optical multiplexing circuit. CONSTITUTION:The wavelength multiplex light signal subjected to an attenua tion effect during propagation in an optical fiber 1 is separated by each wave length in the wavelength separating circuit 4 and is made incident to the optical fiber amplifier circuits 6-1 to 6-n. Exciting light amplifies the light signal when the exciting light is made incident from a light source 5 to the optical fiber amplifier circuits 6-1 to 6-n at this time. The degraded intensity is then recovered and the light is emitted from the optical fiber amplifier circuits 6-1 to 6-n. The light signal is not emitted from the optical fiber amplifier circuits 6-1 to 6-n if the exciting light is not made incident to the optical fiber amplifier circuits 6-1 to 6-n and, therefore, the light signal of the one wavelength lambda1 is selected from, for example, the wavelength multiplex light signal and is taken out to the light receiving circuit 3 via the optical multiplexing circuit 7.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention is an optical wavelength selection method that selectively passes an optical signal of a desired wavelength from wavelength-multiplexed optical signals transmitted using an optical fiber as a transmission medium. It is related to circuits.

(Prior Art) FIG. 2 is a block diagram of a conventional optical wavelength selection circuit. Second
In the figure, 1 is an optical fiber for transmission line, with wavelengths λ1 to λ
. A so-called wavelength-multiplexed optical signal in which the respective optical signals are wavelength-multiplexed is transmitted. 2 is an optical wavelength selection circuit consisting of a semiconductor laser, and when a bias current near the threshold current is applied,
It selectively amplifies and passes only the input light that matches the oscillation mode.

3 is an optical receiving circuit that receives the optical signal that has passed through the optical wavelength selection circuit 2;

In such a configuration, a wavelength-multiplexed optical signal transmitted through an optical fiber is selectively passed through an optical wavelength selection circuit 2 for a desired single wavelength optical signal, and this optical signal is sent to an optical receiving circuit 3. received.

(Problem to be Solved by the Invention) However, according to the above configuration, the amplification characteristic of the semiconductor laser constituting the optical wavelength selection circuit 2 for the passing optical signal depends on the polarization of the input light and is 1/100 Since it requires highly accurate temperature control on the order of degrees Celsius, there are disadvantages in that the output level fluctuates easily and temperature control is complicated.

In addition, the usable wavelength band width is limited by the resonant wavelength interval of the semiconductor laser and the variable width of the resonant wavelength. It had the disadvantage of being very narrow, at 2vm.

The present invention has been made in view of the above circumstances, and its purpose is to transmit an optical signal of a desired wavelength from a wavelength multiplexed optical signal transmitted using an optical fiber as a transmission medium, without depending on polarization. Another object of the present invention is to provide an optical wavelength selection circuit that can selectively pass light with little loss and can be used in a wide wavelength band.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a wavelength demultiplexing circuit that separates wavelength-multiplexed optical signals transmitted using an optical fiber as a transmission medium into wavelengths, A plurality of rare earth element-doped optical fiber amplifier circuits input the separated optical signals and increase or decrease the optical signal intensity according to the input excitation light intensity, and the optical signals that have passed through the optical fiber amplifier circuits are combined. Equipped with a light merging circuit.

(Function) According to the present invention, a wavelength-multiplexed optical signal transmitted using an optical fiber as a transmission medium enters the wavelength demultiplexing circuit in a state in which the intensity is reduced due to a certain attenuation effect while propagating through the optical fiber. be done. The wavelength-multiplexed optical signal input to the wavelength demultiplexing circuit is separated for each wavelength, and each optical signal is input to the corresponding rare earth element-doped optical fiber amplifier circuit.

At this time, if the pumping light is incident on the rare earth element-doped optical fiber amplifier circuit with a predetermined intensity, the pumping light excites the rare earth element doped in the optical fiber while propagating through the rare earth element-doped optical fiber amplifier circuit. . Accordingly, the optical signal is amplified with a predetermined gain, the reduced intensity is recovered, and the optical signal is emitted from the rare earth-doped optical fiber amplifier circuit.

On the other hand, if the excitation light is incident on the rare-earth element-doped optical fiber amplifier circuit with an intensity below a predetermined level, or if the excitation light is not incident on the optical fiber amplifier circuit, the optical signal will pass through the optical fiber while propagating through the rare-earth element-doped optical fiber amplifier circuit. and is not emitted from the rare earth element-doped optical fiber amplifier circuit.

In this way, the optical signals selectively amplified and emitted by the respective rare earth element-doped optical fiber amplifier circuits are then input to the optical combining circuit, combined, and output from the optical wavelength selection circuit.

(Embodiment) FIG. 1 is a block diagram showing an embodiment of an optical wavelength selection circuit according to the present invention, and the same components as those in FIG. 2 showing a conventional example are denoted by the same reference numerals. That is, 11 is an optical fiber for transmission line, and the wavelength band is 1.5 μm (λ ~ λ, λ1≠λ2≠
,...,≠λ. ) are wavelength-multiplexed, and a wavelength-multiplexed optical signal is transmitted. 3 is an optical receiving circuit, and 4 is a wavelength demultiplexing circuit, which separates wavelength-multiplexed optical signals transmitted using the optical fiber 1 as a transmission medium into wavelengths. 5 is an excitation light source;
For example, it is made of a semiconductor laser with an oscillation wavelength of 1.48 μm band (λ), and emits excitation light at a predetermined intensity (several tens of mW).

6-1 to 6-n are rare earth element-doped optical fiber amplifier circuits (hereinafter referred to as optical fiber amplifiers) whose number corresponds to the number of separated wavelengths, in which silica-based optical fibers are doped with a rare earth element, such as erbium (hereinafter referred to as Er). ) is added at a predetermined concentration. These optical fiber amplifier circuits 6
-1 to 6-n amplify each optical signal in the 1.5 μm wavelength band separated by the wavelength separation circuit 4 when the pumping light from the pumping light source 5 is incident at a certain intensity or higher. The amplification factor increases as the intensity of the pumping light increases, and when the injection state of the pumping light is stopped, it becomes an absorption medium for optical signals in the wavelength band of 1.5 μm (Reference: K, II Agimoto, a
t, at, ”A 2121v N0N-RIEP
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(see Uston, Feb. L989).

7 is an optical combining circuit, and optical fiber amplifier circuits 6-1 to 6-n
selectively amplified by these optical fiber amplifier circuits 6-
The optical signals emitted from 1 to 6-0 are combined and output to the optical receiving circuit 3.

Next, the operation according to the configuration described in ``1'' will be explained.

A wavelength-multiplexed optical signal transmitted using the optical fiber 1 as a transmission medium is subjected to a certain attenuation effect while propagating through the optical fiber 1, and enters the wavelength demultiplexing circuit 4 in a state in which the intensity is reduced. The wavelength multiplexed optical signal inputted to the wavelength demultiplexing circuit 4 is separated for each wavelength, and each optical signal is sent to the optical fiber amplifier circuits 6-1 to 6-6.
−n respectively.

At this time, if the pump light source 5 enters the pump light with a predetermined intensity into the optical fiber amplifier circuits 6-1 to 6-n, the pump light is propagating through the optical fiber amplifier circuits 6-1 to 6-n. to excite the rare earth elements added to the optical fiber. Along with this, the optical signal is amplified with a predetermined gain, the reduced intensity is recovered, and the optical fiber amplifier circuit 6-
1 to 6-n.

On the other hand, if the pumping light from the pumping light source 5 is not incident on the optical fiber amplifier circuits 6-1 to 6-n, the optical signal will enter the optical fiber while propagating through the optical fiber amplifier circuits 6-1 to 6-n. It is absorbed and is not emitted from the optical fiber amplifier circuits 6-1 to 6-n.

The optical signals selectively amplified and outputted in the optical fiber amplifier circuits 6-1 to 6-0 in this manner are then input to the optical combining circuit 7 and combined. The optical signals combined by the optical combining circuit 7 are received by the optical receiving circuit 3, converted into electrical signals, and then subjected to predetermined processing.

Therefore, by inputting the pumping light from the pumping light source into only one specific optical fiber amplifier circuit, for example, the optical fiber amplifier circuit 6-1, one wavelength-multiplexed optical signal transmitted through the optical fiber 1 can be extracted. Select an optical signal of wavelength λ1,
It can be received by the optical receiving circuit 3 via the optical combining circuit 7. Furthermore, the intensity of the optical signal of wavelength λ1 is increased by the amplification effect of the optical fiber amplifier circuit 6-1, so that the optical signal can be accurately received by the optical receiving circuit 3 with high sensitivity.

As described above, according to the embodiment of the bookcase 1, the optical fiber 1
A wavelength multiplexed optical signal transmitted as a transmission medium is separated into wavelengths by a wavelength demultiplexing circuit 4, and the optical signal intensity of each of these separated optical signals is amplified or attenuated depending on the incident state of the pumping light. By inputting the Er-doped optical fiber into the Er-doped optical fiber amplifier circuits 61 to 6-n, only the optical signal of the desired wavelength is selectively extracted and received by the optical receiving circuit 3 via the optical combining circuit 7. As a result, an optical wavelength selection circuit is realized that has no polarization dependence, has relaxed temperature control conditions, has low loss, and can be used in a wide wavelength band.

In this example, Er (erbium) was used as an example of the rare earth element added to the optical fiber.
It goes without saying that the present invention is not limited to this, and the same effect as described above can be obtained even if an optical fiber amplifier circuit doped with other rare earth elements is used. In this case, the wavelength of the excitation light is appropriately selected depending on the rare earth element to be added.

(Effects of the Invention) As explained above, according to the present invention, there is provided a wavelength demultiplexing circuit that separates wavelength-multiplexed optical signals transmitted using an optical fiber as a transmission medium into wavelengths, and A plurality of rare-earth element-doped optical fiber amplifier circuits that receive optical signals and increase or decrease the intensity of the optical signals according to the intensity of the input excitation light, and an optical combining circuit that combines the optical signals that have passed through the optical fiber amplifier circuits. This makes it possible to selectively extract an optical signal of a desired wavelength from a wavelength-multiplexed optical signal transmitted through an optical fiber without depending on polarization and with low loss. This has the advantage of being able to provide an optical wavelength selection circuit with a wide wavelength band.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of an optical wavelength selection circuit according to the present invention, and FIG. 2 is a block diagram of a conventional optical wavelength selection circuit. In the figure, 1... Optical fiber for transmission line 1. 3... Optical receiver circuit, 4... Wavelength separation circuit, 5... Light source for excitation, 6
1 to 6-n...Er (rare earth element) doped optical fiber amplifier circuit, 7... Optical merging circuit.

Claims (1)

[Scope of Claims] A wavelength demultiplexing circuit that separates a wavelength-multiplexed optical signal transmitted using an optical fiber as a transmission medium into wavelengths, and an optical signal wavelength-separated by the wavelength demultiplexing circuit that enters the optical signal and determines the intensity of the optical signal. A plurality of rare earth element-doped optical fiber amplifier circuits that increase or decrease the intensity of the optical fiber according to the intensity of the incident pumping light, and an optical combining circuit that combines optical signals that have passed through the optical fiber amplifier circuits. selection circuit.