JP3063515B2 - Optical direct amplifier - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical direct amplifying apparatus, for example, an optical FDM (Frequency Division Multiple Multiple).
x) Transmission system and optical SCM (Sub Carrior Multiple
x) It relates to an optical direct amplification device used in a transmission system.

[0002]

2. Description of the Related Art An optical direct amplifying device is an optical-to-optical converter and an optical / optical converter.
Compared to a conventional 3R repeater in which electrical conversion is interposed, the amplifier is a simple configuration and exhibits equal or higher performance, and therefore, research and development of an optical communication system using the same is actively pursued.

[0003] There are various uses (installation locations) of the optical direct amplifying device in the optical communication system, and functions desired for the device differ according to the respective uses. For example, in an optical FDM transmission system or the like, an optical direct amplification device whose amplification factor can be set arbitrarily is required.

That is, in an optical FDM transmission system, 1
In this optical fiber, light multiplexed with optical signals having different wavelengths is propagated, and it is branched in a receiving station (relay station).
For example, distribution to each receiver is performed. In such a system, usually, the length of an optical fiber installed between an optical branch circuit for branching light and each receiver,
The number of optical circuits differs for each receiver, and each receiver will receive a different level of optical signal. For this reason, there is a need for an amplifier capable of amplifying optical signals that have been attenuated to different degrees to the same level on the receiver side, that is, an amplifier capable of amplifying an input optical signal at a desired amplification factor.

Conventionally, in an optical direct amplifying device, the gain can be adjusted by changing a reference voltage for maintaining a constant amplification factor of the optical direct amplifying device.

FIG. 3 shows an outline of a conventional direct optical amplifier. This figure shows an outline of an optical direct amplifying device using a rare-earth-doped optical fiber, focusing on its circuit. In the figure, a variable resistor 13 changes a reference voltage serving as a reference of an amplification factor. Part. The outline of the operation of this optical direct amplification device is described below.

A part of the signal light amplified by the rare earth-doped optical fiber (not shown) is incident on the light receiving element 11, and a voltage corresponding to the light level received by the light receiving element 11 is input to the error amplifier 14. . The error amplifier 14 includes the variable resistor 1
The reference voltage corresponding to the set value of 3 is also input, and the error amplifier 14 outputs a voltage corresponding to the voltage difference between the two. The output of the error amplifier 14 is input to the amplifier 15 and
5 performs a predetermined amplification on the input voltage.

The voltage output from amplifier 15 is used to drive transistors 17 and 18,
Changes the level of light (light supplied as excitation light for the rare earth-doped optical fiber) output from the light emitting element 19 in accordance with the input. The illustrated circuit is a circuit that controls the output of the light emitting element 19 so as to reduce the error voltage. Therefore, when the set value of the variable resistor 13 is changed, the light emission is controlled so that the error voltage decreases. The light level of the element 19 is controlled, and as a result, the amplification factor takes a value corresponding to the set value.

[0009]

In the conventional optical direct amplifying device as described above, it is possible to adjust the amplification factor of the optical signal, but depending on the setting of the variable resistor, an excessively large light emitting element is required. In some cases, a current may flow and the light emitting element may be destroyed.

It is an object of the present invention to provide an optical direct amplifying device which does not cause destruction of a light emitting element even if a user erroneously adjusts an amplification factor.

[0011]

[Means for Solving the Problems]

According to the first aspect of the present invention, there is provided (a) a rare earth-doped optical fiber for amplifying and outputting an input optical signal;
(B) an excitation light source for outputting an excitation light for controlling the amplification factor of the rare-earth-doped optical fiber, (c) amplification factor setting means for setting the amplification factor of the rare-earth-doped optical fiber,
(D) reference voltage output means for outputting a reference voltage according to the amplification rate set by the amplification rate setting means, (e) level detection means for detecting the level of the optical signal output from the rare earth-doped optical fiber, F) an error voltage output means for outputting the difference between the output of the level detection means and the reference voltage as an error voltage; and (g) an optical level output by the excitation light source such that the error voltage output by the error voltage output means is reduced. Light source control means for performing the control of (a), (h) limited voltage output means for outputting a predetermined limited voltage, and (iii) excitation light source control means for an error voltage when the reference voltage exceeds the limited voltage Blocking means for blocking input to the device.

That is, according to the first aspect of the present invention, in the optical direct amplifying device using a rare earth-doped optical fiber, an amplification factor setting for enabling adjustment of a reference voltage used as a reference value in the amplification factor control. Means for preventing amplification control according to the reference voltage when the reference voltage changed according to the set value by the amplification setting means exceeds the limit voltage.

According to a second aspect of the present invention, there is provided (a) a semiconductor laser amplifier for amplifying and outputting an inputted optical signal;
(B) amplification factor setting means for setting the amplification factor of the semiconductor laser amplifier; (c) reference voltage output means for outputting a reference voltage corresponding to the amplification factor set by the amplification factor setting device; Level detecting means for detecting the level of the optical signal output from the laser amplifier; (e) error voltage output means for outputting a difference between the output of the level detecting means and a reference voltage as an error voltage; and (f) error voltage output. Gain control means for controlling the gain of the semiconductor laser amplifier so that the error voltage output by the means is reduced; (g) limited voltage output means for outputting a predetermined limited voltage; And blocking means for blocking the input of the error voltage to the amplification factor control means when the difference exceeds the threshold value.

That is, according to the second aspect of the present invention, in an optical direct amplification device using a semiconductor laser amplifier, an amplification factor setting means for enabling adjustment of a reference voltage used as a reference value for amplification factor control. And blocking means for stopping the gain control according to the reference voltage when the reference voltage changed according to the set value by the gain setting means exceeds the limit voltage.

[0016] In the third aspect of the present invention, a rare earth doped optical fiber for amplifying and outputting the optical signal input (b),
(B) an excitation light source for outputting an excitation light for controlling the amplification factor of the rare-earth-doped optical fiber, (c) amplification factor setting means for setting the amplification factor of the rare-earth-doped optical fiber,
(D) a reference voltage output means for outputting a reference voltage corresponding to the set amplification factor by the amplification factor setting means, (e) the excitation light
A group corresponding to the amplification factor corresponding to the upper limit at which no source destruction occurs
A limit voltage output means for outputting a predetermined limit voltage that matches the reference voltage, and a reference voltage output from the reference voltage output means.
And the limit voltage output by the limit voltage output means.
A voltage selection and output means for selecting and outputting the lower one of these voltages ; (g) a level detection means for detecting the level of an optical signal output from the rare earth-doped optical fiber;
(H) an error voltage output means for outputting the difference between the output of the level detection means and the output of the voltage selection means as an error voltage; and (iii) the excitation so as to reduce the error voltage output by the error voltage output means. An excitation light source control means for controlling the light level output from the light source is provided in the optical direct amplification device.
Let it .

That is, according to the third aspect of the present invention, the optical direct amplifying device using the rare-earth-doped optical fiber is provided with voltage selecting means for outputting the smaller one of the reference voltage and the limit voltage, and the output thereof is provided. Is used as a reference when calculating the error voltage, thereby protecting the light emitting element that outputs the excitation light to the rare earth-doped optical fiber.

According to a fourth aspect of the present invention, there is provided (a) a semiconductor laser amplifier for amplifying and outputting an input optical signal;
(B) a gain setting means for setting the amplification factor of the semiconductor laser amplifier, a reference voltage output means for outputting a reference voltage corresponding to the gain set by the (iii) amplification factor setting means, (d) a semiconductor At the upper limit where laser amplifier destruction does not occur
And limiting the voltage output means for outputting a predetermined limit voltage matches the reference voltage corresponding to a corresponding amplification factor, (e) a reference voltage
Reference voltage output from output means and output from limited voltage output means
Input both of the limiting voltages
A voltage selection output means for selecting the lower, (to)
Level detecting means for detecting the level of the optical signal by the semiconductor laser amplifier is output, (g) and the error voltage output means for outputting the difference between the outputs of the voltage selection means of the level detection means as an error voltage, (viii) the error voltage output means direct light amplification instrumentation and the amplification factor control means for controlling the amplification factor of the semiconductor laser amplifier so that the error voltage output is reduced
To be installed .

That is, in the invention according to the fourth aspect, the optical direct amplifying device using the semiconductor laser amplifier is provided with voltage selecting means for outputting the smaller one of the reference voltage and the limit voltage, and the output is selected. The semiconductor laser amplifier (light emitting element) is protected by using it as a reference when calculating the error voltage.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to embodiments.

FIG. 1 shows an outline of an optical direct amplification apparatus according to an embodiment of the present invention. The optical direct device of the embodiment is different from the conventional optical direct amplifying device described with reference to FIG. 3 in that a shutdown circuit 16, a resistor 20, a comparator 21, and a relay 2 are provided.
2, and as shown in the figure, the shutdown circuit 16
7 is connected so as to control the error voltage supplied thereto. Further, the reference voltage from the variable resistor 13 is input to the comparator 21, and the comparator 21 compares the input voltage with the limit voltage from the variable resistor 20, and according to the comparison result. It is configured to output an electric signal to the relay 22. The relay contact 23 of the relay 22 is connected to the shutdown circuit 16.

In the optical direct amplifying device of the embodiment, an erbium-doped optical fiber is used as the rare earth-doped optical fiber (not shown), a PIN photodiode is used as the light receiving element 11, and a laser diode is used as the light emitting element 19. ing.

The variable resistor 20 is a resistor which is set before assembling the device into an optical communication system, for example, when the optical direct amplifying device is manufactured, and has a reference voltage at which the optical direct amplifying device can operate stably. It is adjusted so that the upper limit is output. The variable resistor 13 is a resistor used for adjusting the amplification factor of the optical direct amplification device after being incorporated in the optical communication system.

When the optical direct amplifying device is configured as described above,
When the reference voltage output in accordance with the set value of the variable resistor 13 is equal to or lower than the output voltage (limit voltage) of the variable resistor 20, the optical direct amplifying device described in the related art is used. The same operation as described above is performed, and the input optical signal is amplified by an amount corresponding to the reference voltage.

When the setting of the variable resistor 13 exceeds the limit voltage, the relay 12 is activated, and as a result, the shutdown circuit 16 blocks the input of the output of the amplifier 15 to the transistor 17. Thus, the light emitting element 19 is protected.

As described above, according to the optical direct amplifying device of the embodiment, even if the user erroneously adjusts the gain, the light emitting element is not destroyed.

It is to be noted that the light emitting element is not destroyed by merely limiting the range of the resistance that can be taken by the variable resistor 13 without limiting using the variable resistor 20 as in the embodiment. Can be. However, generally used variable resistors have characteristic variations between the elements, so that in order to prevent the destruction of the light emitting element, a variable resistor having a setting range narrower than necessary must be used. For this reason, in such a configuration, the adjustment range of the amplification factor of the optical direct amplifying device becomes narrow. On the other hand, in the optical direct amplifying device of the present invention, since the circuit for setting the amplification factor and the circuit for limiting the amplification factor are different, the circuit for the former has any variation. Is used, a device capable of adjusting the amplification factor within a predetermined range can be obtained, and the adjustment range of the device does not become narrow due to the limitation on the characteristics of the variable resistor.

Although the optical direct amplifying device of the embodiment uses a rare earth doped optical fiber, the present invention is also applicable to an optical direct amplifying device using a semiconductor laser amplifier. In this case, a semiconductor laser amplifier is used in a portion corresponding to the light emitting element 19 in FIG.
If it is configured to receive the output light of the semiconductor laser amplifier (although a slight change in the circuit is necessary), even if the amplification factor is erroneously adjusted, light is directly amplified without destruction of the light emitting element. A device can be obtained.

Modification

Further, without using a shutdown circuit, FIG.
With the configuration shown in (1), even if the user makes an error in the adjustment of the amplification factor, it is possible to obtain an optical direct amplification device in which the light emitting element is not destroyed.

In the optical direct amplifying device of the modified example, as shown, outputs from the variable resistors 13 and 20 are input to the switching circuit 25, and the switching circuit 25
Are input to the error amplifier 14. The switching circuit 25 is a circuit that outputs a signal having a smaller voltage among the two inputs.

In this optical direct amplification device, the variable resistor 13
The reference voltage output according to the set value of the variable resistor 2
When the voltage becomes higher than the limit voltage defined by 0, the limit voltage is supplied to the error amplifier 14 instead of the reference voltage. Therefore, even if the variable resistor 13 is erroneously set, the current flowing through the light emitting element 19 does not exceed a certain value, and the light emitting element is not destroyed. Although the illustrated apparatus uses a rare-earth-doped optical fiber, this technique can be applied to a case where a semiconductor laser amplifier is used.

[0033]

As described above , according to the first to fourth aspects of the present invention , even if the user erroneously adjusts the amplification factor, the issuing element is not destroyed. Further, since the circuit for setting the limit voltage is provided separately from the circuit for setting the gain by the user, an inexpensive circuit can be used as the gain setting circuit. Further, according to the third and fourth aspects of the present invention,
For example, the voltage selection output means inputs both the reference voltage and the limit voltage.
To select and output the lower of these voltages.
Therefore, in normal cases, the reference voltage is output and this voltage
The amplification factor can be controlled by the excitation light source.
Or a voltage that would cause destruction of the semiconductor laser amplifier
Before switching to the limit voltage,
Ensure the reliability of these devices while enabling width ratio control.
There is an advantage that can be maintained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an optical direct amplification device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of an optical direct amplification device according to a modification.

FIG. 3 is a circuit diagram showing a configuration of a conventional optical direct amplification device.

[Explanation of symbols]

 Reference Signs List 11 light receiving element 12 resistor 13, 20 variable resistor 14 error amplifier 15 amplifier 16 shutdown circuit 17, 18 transistor 19 light emitting element 21 comparator 22 relay 23 relay contact 25 switching circuit

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-4-25822 (JP, A) JP-A-3-100527 (JP, A) JP-A-3-62022 (JP, A) JP-A-4- 118637 (JP, A) JP-A-2-308581 (JP, A) JP-A-6-268306 (JP, A) JP-A-7-38187 (JP, A) JP-A-5-67032 (JP, U) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01S 3/10 H01S 3/06-3/07 H01S 5/00-5/50 H04B 10/00-10/28

Claims (4)

(57) [Claims] 1. A rare earth-doped optical fiber for amplifying and outputting an input optical signal, an excitation light source for outputting excitation light for controlling an amplification factor of the rare-earth-doped optical fiber, Amplification factor setting means for setting an amplification factor; reference voltage output means for outputting a reference voltage according to the amplification factor set by the amplification factor setting device; and a level of an optical signal output from the rare earth-doped optical fiber. Level detection means for detecting, error voltage output means for outputting a difference between the output of the level detection means and the reference voltage as an error voltage, and the excitation light source so that the error voltage output by the error voltage output means is reduced. Pumping light source control means for controlling the light level to be output; limited voltage output means for outputting a predetermined limited voltage; and wherein the reference voltage exceeds a limited voltage. In the case it was,
Blocking means for blocking the input of the error voltage to the pumping light source control means. 2. A semiconductor laser amplifier for amplifying and outputting an input optical signal, gain setting means for setting the gain of the semiconductor laser amplifier, and a gain set by the gain setting means. Reference voltage output means for outputting a corresponding reference voltage; level detection means for detecting the level of an optical signal output from the semiconductor laser amplifier; and outputting the difference between the output of the level detection means and the reference voltage as an error voltage. Error voltage output means, gain control means for controlling the gain of the semiconductor laser amplifier so that the error voltage output by the error voltage output means is reduced, and limit voltage output means for outputting a predetermined limit voltage; When the reference voltage exceeds the limit voltage,
Blocking means for blocking the input of the error voltage to the gain control means. 3. A rare earth-doped optical fiber for amplifying and outputting an input optical signal, an excitation light source for outputting excitation light for controlling an amplification factor of the rare earth-doped optical fiber, and a rare earth-doped optical fiber. Amplification factor setting means for setting an amplification factor; reference voltage output means for outputting a reference voltage according to the amplification factor set by the amplification factor setting device; and amplification corresponding to an upper limit at which destruction of the excitation light source does not occur. To rate
Limiting voltage output means for outputting a predetermined limit voltage that matches a corresponding reference voltage; and a reference voltage and a limit voltage output from the reference voltage output means.
Input both of the limiting voltages output by the
Voltage selection output means for selecting and outputting the lower one of the voltages, level detection means for detecting the level of an optical signal output from the rare-earth-doped optical fiber, and output of the level detection means and the voltage selection means. Error voltage output means for outputting a difference between outputs as an error voltage; and excitation light source control means for controlling a light level output by the excitation light source so that the error voltage output by the error voltage output means is reduced. An optical direct amplifying device, characterized in that: 4. A semiconductor laser amplifier for amplifying and outputting an input optical signal, gain setting means for setting the gain of the semiconductor laser amplifier, and a gain set by the gain setting means. A reference voltage output means for outputting a corresponding reference voltage ;
Limiting voltage output means for outputting a predetermined limit voltage that matches a reference voltage corresponding to the amplification factor, and a reference voltage and a limit voltage output from the reference voltage output means.
Input both of the limiting voltages output by the
Voltage selection output means for selecting and outputting the lower one of the voltages; level detection means for detecting the level of the optical signal output by the semiconductor laser amplifier; output of the level detection means and output of the voltage selection means Error voltage output means for outputting the difference between the two as an error voltage; and gain control means for controlling the gain of the semiconductor laser amplifier so that the error voltage output by the error voltage output means is reduced. Optical direct amplification device.