JPS5854745A - Automatic gain adjusting system for optical switch system - Google Patents

Abstract

PURPOSE:To perform gain adjustment of an O/E optical power, by switching a gain adjusting path preset to a corresponding photoelectric conversion section (O/E) simultaneously with the switching of an input switch, through the system transmitting a combined signal of input and output transmission lines to an optical switch and the O/E section at the same time. CONSTITUTION:Cameras 1a-1d transmit caught information to an electrooptic conversion sections E/O1-E/O4 in an electric signal, where the signal is converted into an optical signal. The optical signal is transmitted to an optical switch 11 of a reception sensor 9 via transmission lines 7a-7d. The optical switch 11 connects the transmission line to an output transmission line 13 through the switching operation and introduces the signal to an photoelectric conversion section O/E 17 via the transmission line 13 and a photodetector 15. The O/E 17 converts light into electric signals and transmits the signals to a television 21. A keyboard 23 transmits an instruction signal of the combination of the output transmission line 13 and the input transmission lines 7a-7d, and when a key is depressed, an instruction signal is transmitted to a controller 25.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic gain adjustment method for an optical switch system in an optical communication system.

In an optical communication system, information obtained from an information source is
Broadly speaking, it is often transmitted along the following route. That is,
The electrical signal of information is converted into an optical signal by an electrical-to-optical converter (hereinafter simply referred to as "optical fiber cable"), and then an optical input transmission line (optical fiber cable), an optical switch system, and an optical output transmission line (optical fiber cable) are used. via the optical-to-electrical converter (
(hereinafter simply referred to as OA), the signal is converted back into an electrical signal and transmitted to a demodulator or the like. The optical switch system often has a plurality of transmission lines on the input side and the output side, for example, n and m transmission lines, and these are mutually switched to form nXm sets of input and output transmission lines. Combinations are possible. In this case, between the above optical switch on the transmitting side and the above optical switch on the receiving side 1
Normally, the distances, ie, lengths, of each input transmission path are different. Since the loss of the transmitted light increases in proportion to the length of the transmission path, the optical loss in the n input transmission paths varies in magnitude depending on the length. Therefore, the levels of optical power input to the optical switch system from the n input transmission lines are different from each other.

Furthermore, in optical switches, loss of transmission optical power occurs due to connection loss and the like. Furthermore, loss of transmitted light/power also occurs in the output transmission line from the optical switch to the o/rg. Therefore, there will be differences in the level of optical loss for each combination of input and output transmission lines, so the light input to the O/E
The level of the signal varies greatly depending on the combination of input and output transmission paths. On the other hand, in the above-mentioned 0/E, it is necessary to convert these optical signals and keep the level of the electrical signal to be output at a predetermined constant value before sending it out for demodulation or the like. Also, the optical loss is 1
In the case of electricity, dB is equal to 2 dB, so 0 input light, 1? Depending on the magnitude of the power, the output electrical level of the OA will be greatly affected. Therefore, in order to keep the output electrical level of this OA constant, it is necessary to adjust the gain of the OA power over a wide range.

In conventional optical switch systems of this type, the optical switch simply switches input and output transmission paths, and an automatic gain control element (hereinafter simply referred to as an AGC element), such as a field effect transistor (FET), is used in the O/A. ) and an aparanse diode (APD), etc., and an automatic gain adjustment function is added to 0/P2 itself.

However, in general, such an AGC element alone cannot cover a wide range of gain adjustment, so in conventional optical switch systems, for example, optical loss
Adjustment over a large range of 0 dB, ie 20 dB at the electrical level, is very difficult.

However, this conventional optical switch system cannot automatically adjust the gain of the 0/E input optical power, which varies depending on the combination of input and output transmission lines, according to each combination of input and output transmission lines. The output electrical level cannot be kept well constant. As a countermeasure for this, an optical attenuator (optical ATT) is installed between each input connector of the optical switch and the input transmission line.
) may be used as an intervening device to adjust the O/E input optical power to the same root 1k. However, in this case, the optical attenuator is very expensive and there is a problem with economic efficiency, and the ratio of the strength of the signal and noise from each
In other words, there are undesirable problems such as adjusting the S/N ratio to the S/N ratio of the transmission line which has the worst S/N ratio, and this is not a fundamental solution.

The purpose of the present invention is to solve the drawbacks of the prior art as described above.
An object of the present invention is to provide an inexpensive automatic gain adjustment method for an optical switch system in which the electrical output level of /E is kept constant.

In order to achieve this object, according to the present invention, in an optical switch system consisting of n input transmission lines and m transmission lines, the switching combination information of the input transmission lines and output transmission lines is By simultaneously transmitting signals to the optical switch in the optical switch and the optical-to-electrical converter provided on the output transmission path side, the electrical output level of the optical-to-electrical converter can be increased in any combination of input and output transmission paths in the optical switch. An automatic gain adjustment power formula for an optical switch system is provided in which the gain adjustment corresponding to each of the input/output transmission lines of each combination is performed in the above-mentioned electrical-to-electrical converter so that the gain is constant.

The following is an example of this book with attached drawings.Request for details 1
to invent.

FIG. 1 is a diagram showing an example of application of the method according to the present invention, and is an example of application in an optical communication system where the number of human power and output transmission lines of an optical switch system is 4 to 1. The optical communication system shown in Figure 1rIJ can be used, for example, for purposes other than road monitoring and river monitoring, in which monitoring information from each television camera is selected at a reception center and displayed on a monitor television.

In the figure, 1 a , ], b + I C and 1
diJ TV Kamishi, 3a.

3b, 3c and 3d are electric line 18, l) a 15
b +5c and 5d are electrical-to-optical converters, respectively.
.

Elo 2, Elo 3 and Shizu 4.7a,'lb
, 7a and 7d are optical signal input transmission lines (nine fiber cables 09 is a receiving center, 11 is an optical switch, 13←'', optical signal output transmission line, 15 is a light receiving element, 17 is 0/E, 19
21 (Umonitor TV, 23 Keen Jζ-do, 214, 'Ichiki Iif-■ Yusen, 25 Jinjo, j-n 11; switch and O/AC1li control device, Then 27.28 is the electric signal line 4.Camera 1a
transmits the captured information as an electric signal to Elo 1 of 5a via the signal line 3a. Elo 1 converts this electrical ID into optical signal i4""f', and sends it to the optical switch 11 of the receiving center 9 via the optical signal input transmission line 7a. The source switch 11 is a known one and connects the input transmission line 7a to the output transmission line 13 by a switching operation, and connects the input transmission line 7a to the output transmission line 13.
3 and the light receiving element 15 to transmit the optical signal 0/E, 17
lead to. The 0/E 117 converts this optical signal train into an electrical signal again and sends it to the television 21, and the television 21 projects and outputs the above information based on this electrical signal. Note that information transmission from the cameras lb, lc, and 1d other than those described above to the television 21 is performed in exactly the same manner as described above.

The keyboard 23 sends out command signals for the combinations of the input transmission lines 7a, 7b, 7c, and 7d and the output transmission line 13, and when a key for each predetermined combination setting is pressed, a command signal is sent via the electric signal line 24. A command signal is sent to the control device 25. Based on this command signal, the control device 25 sends a combination signal of the input/output transmission line, for example, a combination of signal 1 and 0/E to the optical switch 11 via the electrical signal line 27, and at the same time sends a combination signal of the input/output transmission path to the optical switch 11 via the electrical signal line 27. The combined signal of this input/output transmission line is also sent out to 17 O/Es via. Based on this combination signal, the optical switch 11 switches the input/output transmission path to a combination corresponding to Ig, for example, Vj:, Elo 1→0/E, while OA switches the transmission path F, 1 of the above combination.
The optical power input through the 01→sensor is converted into an electrical signal, and the gain adjustment amount of this electrical signal is set in advance, and the gain is automatically adjusted by the Elo 1→0 circuit installed inside the α. and sends it to the electrical signal line 19 as a constant electrical output level.

FIG. 2 is a block diagram of an example of the circuit shown in FIG. In the figure, 29 is a preamplifier, 29a is a feedback resistor, 30 is an output amplifier, and the following are according to the present invention: 31.32ij relay, 33a is an attenuator A, 3
3b is an attenuator B, 33c is an electric signal line, and 33d is an amplifier. Note that the symbols other than those mentioned above in the figure indicate the same parts as the symbols shown in FIG.
33a, attenuator B, 33b, electric signal line 33a, and amplifier 33d. These paths correspond to the four combination input/output transmission paths in Figure 1, and for example, V in Figure 1.
Attenuators A and 3 are used for the transmission line of O1→O/E combination.
A 3m path is supported.

In this case, the attenuator A, 33a is set so as to calculate in advance the optical power loss in the combined transmission line from 1 to OA and adjust the gain accordingly.
It serves as a gain adjustment path for the combined transmission line of lo1→o7g.

In this way, by adjusting the gain commensurate with the loss of the E input optical power, the 0/E electrical output level can be kept very well constant.

Next, the operation in FIG. 2 will be explained. When the control device 25 receives a command signal for a combination of input/output transmission paths from the keyboard 23, the control device 25 correspondingly sends a combination signal of input/output transmission paths stored in advance, for example, a combination signal of VO1→0/E. The signal is sent to the optical switch 11 via the line 27 and at the same time to the relays 31 and 32 via the signal line 28. Therefore, the relays 31 and 32 are connected to the attenuator A corresponding to the E101→0 transmission line in conjunction with the switching operation of the optical switch 11.
.

Connect the path 33a. Then, the Φ main input optical power via the transmission line of the combination vo1→OA is transmitted to the light receiving element 15.
, the preamplifier 29 and the like, the signal is converted into an electrical signal, amplified, and guided to the relay 31.

Relays 31 and 32 are already connected to attenuator A as described above.

Since the path 33a is connected, the electrical signal is automatically gain-adjusted on this path and is guided to the signal line 19 via the amplifier 30. For other combinations of input/output transmission paths, automatic gain adjustment corresponding to the combination is performed in the same manner as above.

FIG. 3 shows a second example of application of the present invention to an optical switch system having three input and three output transmission lines. In the figure, 13a, 13b, 13c are output transmission lines, 15a
, 15b, 15c are light receiving elements, 17a, 17b
, 17c are O/El, respectively.

0/E 2 , O/E 3.28a , 28b , 2
Reference numeral 8c indicates an electric signal line, and the symbols other than those mentioned above indicate the same parts as those shown in FIG. In this case, the combinations of input and output transmission lines have only been increased to 9 sets (3x3), and the basic configuration and operation are exactly the same as the first application example shown in Figures 1 and 2 above. be.

As described above, according to the present invention, the combined signal of the input and output transmission lines is sent to the optical switch and the O/E at the same time. Correspondingly, it is also possible to switch the gain adjustment path preset in the OA to perform automatic gain adjustment of the OA input optical power.

Therefore, there is no need to prepare expensive AGC elements over a wide range as in the past, and this automatic gain adjustment method for optical switch systems is inexpensive and allows good gain adjustment over a wide range of loss differences between O/IE input light and power. can be realized.

[Brief explanation of the drawing]

FIG. 1 is a first application example of the present invention, which shows an example of application to an optical switch system in which input and output transmission lines are 4 to 1, and FIG. 2 is a circuit inside the OA shown in FIG. 1. FIG. 3 is a block diagram showing a second application example of the present invention, which is a diagram showing an application example to an optical switch system having three input and three output transmission lines. 5m, 5b 5c, 5d=・'Nausea-light conversion part (El
o1, glo2, Elo3, Elo
4), 7a, 7b. 7e, 7d...Input transmission line, 11...Optical switch, 13.13a, 13b, 13c...Output transmission line, 1
5, 15a, 15b, 15c-light receiving element, 17°17a,, 17b, 17a
=Light-to-electricity converter (0/E. OAl, O/E 2 , O/]BE 3), 19
, 24, 27° 28... Electrical signal line, 23... Key is - de, 25... Optical switch and intermediate control device, 29
...Preamplifier, 30...Output amplifier, 31.32
...Relay, 33a...Attenuator A, 33b...Attenuator B, 33c...Electric signal line, 33d...Amplifier. Patent applicant Fujitsu Limited Patent attorney Akira Aoki Patent attorney Kari Nishidate Patent attorney 1) Yukio Patent attorney Akira Yamaguchi

Claims (1)

[Claims] 1. In an optical switch system with n input transmission lines and m output transmission lines, switching combination information of the input transmission line and output transmission line is transmitted between the optical switch in the optical switch system and the optical switch provided on the output transmission line side. - The input/output transmission of each combination is made such that the electrical output level of the optical-to-electrical converter is constant in any combination of input/output transmission paths in the optical switch by simultaneously sending the signal to the electrical converter. The gain adjustment corresponding to each path is applied to the above light.
An automatic gain adjustment method for optical switch systems that uses an electrical conversion section.