JPS5834638A - Direction control light transmitting device in time division - Google Patents

Abstract

PURPOSE:To obtain time division type two-way transmission system by connecting an optical fiber for transmission with a light transmitting and receiving section through an optical switch. CONSTITUTION:Continuous transmitting information obtained through a transmitting information line 2' is converted to a high speed light burst signal by a speed changing section 1 and a light transmitting signal generating section 9 and sent out to an optical fiber for transmission 14 through an optical switch 12 and received by receiving side's device 15 having the same constitution. A high speed light signal sent from the device 15 of the other end of the line during receiving time zone is received by a light receiving signal detecting section 10 through an optical switch 12 and the speed is changed by a speed changing section 1 so as to make it continuous receiving information, and sent to a receiving information line 3'. Changing of transmitting time zone and receiving time zone is performed by switching optical connection of a terminal F and T or R by changing the signal applied to an optical switch change-over control signal terminal 13.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmission method in which eleven communication transmission lines are used as bidirectional transmission lines in a time-division manner, and the transmission line optical fibers and the transmitter/receiver are switched in 1b%. It is related to the device.

A time-division directional control optical transmission device is being considered as an arithmetic subscriber line transmission system that transmits bidirectional digital signals using a pair of two-wire cables (IEICE Study Group Material 087B-20 Reference No. ). FIG. 1 shows the configuration of a direction control section using this method. In this figure, 1 is a speed converter, 2 is a transmission signal line, 3 is a reception signal line, 4 is a high-speed switch, 5 is a transmission/reception switching control signal terminal, 6 is an amplifier, 7 is a matching box, and 8 is a 2II
formula kef.

It is le. By switching the 2-wire cable 8Fi high-speed switch 4, it is used as a transmitting cable and a receiving cable in a time-sharing manner. The continuous transmission information is converted by the speed converter IK into a high-speed signal that fits within the transmission time slot and is sent out. The discontinuous high-speed signal received during the reception time period is speed-converted by the speed conversion section 1 so that it becomes continuous reception information. High-speed switch 4 switches between sending time zone and receiving time zone
This is done under the control of This allows bidirectional digital transmission using a pair of 2@2 cables. However, there are the following problems in obtaining good transmission characteristics with this method.

1) The signal bit rate is, for example, about 144 bits/second even for audio only, and it cannot be used due to reflections unless impedance matching between the transmitter/receiver and the transmission path is well achieved. However, generally the length of the telephone subscriber line is
Distributed over hundreds of meters to several kilometers,
The impedance of the two-wire cable changes, and it is difficult to adjust the matching in the matching box 7 of FIG. 1 to the best point among an unspecified number of subscribers.

2) #- with a two-wire cable designed for analog signals
iCrosstalk occurs and the waveform of the digital signal deteriorates.

5) Two-wire cables have large losses (for example, 46 dB over a 5 km length) and require bidirectional relay amplification for distant subscribers, which is expensive.

The above problems become serious drawbacks when transmitting higher-speed signals such as facsimiles and paintings. Furthermore, when optical fiber subscriber lines are introduced, they include transformers and other circuits unsuitable for transmitting optical signals, so this system cannot switch the direction of optical signal transmission.

SUMMARY OF THE INVENTION An object of the present invention is to provide a system suitable for subscriber lines using optical fibers, and for time-divisionally transmitting bidirectional signals over a single communication line.

The present invention is characterized in that time-minute bidirectional transmission is possible by coupling a transmission optical fiber and an optical transmitting/receiving section via an optical switch.

The drawings will be explained in detail below.

FIG. 2 is a block diagram of an apparatus according to an embodiment of the present invention. The speed switching section IFi is connected to a device not shown in the figure by a transmission information line 2' and a reception information line 3', and the transmission information is seen in the optical transmission signal generation section 9, and the reception information is sent to the optical reception signal detection section 10.
given from. This optical transmission signal generation section 9 and optical reception signal detection section 10Kij.

An optical switch 12 is connected via a connecting optical fiber 11. This optical switch 120 control signal is given from the terminal 13, and this optical switch 12 is connected to the transmission optical fiber 1.
Connected to one end of 4.

The other end of the optical fiber 14 is connected to a counterpart device 15 having a similar configuration to the device shown in FIG. Further, the optical switch 12 responds to a control signal given to the terminal 13.
It operates so as to alternately connect the optical fiber 14 to the optical fiber 11 connected to the terminal TK and to the optical fiber 11 connected to the terminal RK. The continuous transmission information obtained through the transmission information s2/ is converted into a high-speed optical burst signal by the speed converter 1 and the optical transmission signal generator 9, and is sent to the transmission optical fiber 14 through the optical switch 12 during the transmission time period. will be sent to. The high-speed optical burst signal sent during the reception time is passed through the optical switch 12 to the optical reception signal detection section 10.
The received information is detected by the speed converter 1, and the speed is converted so that the received information is continuous in the speed conversion section 1, and then sent to the received information Iw3'. The transmission time period and the reception time period are switched by changing the signal applied to the optical switch switching control signal terminal 13 to switch the optical coupling between the terminal ν of the optical switch 12 and the terminal T or terminal R. The timing of this connection switching can be realized using the same method as in the conventional time-division direction control type transmission system. For example, this is possible by managing the burst cycle, which is the sum of the transmission time zone, reception time zone, and transmission delay time, in one of the nine connected terminal devices, and synchronizing the other terminal device with this.

FIG. 5 shows a configuration example in which the optical switch 12 is realized by a 2×2 type voltage-controlled directional coupler. Electro-optic crystal substrate 2
Two optical waveguides 21 and 22 having the same optical characteristics are formed above the optical waveguide 0 . The intermediate portions of these optical waveguides 21 and 22 constitute a coupling region that is close to and parallel to each other, and in the coupling region, between the control electrode 23 on the substrate 20 between the optical waveguides 21 and 220 and the electrode 24 outside thereof. A control voltage from the optical switch switching control signal terminal 13 is applied to. By appropriately changing the length of the coupling region and the control voltage, we can achieve a state in which the waveguide ends a and d and waveguide ends C are optically coupled, and As shown in FIG. 4), it is possible to create a state in which the waveguide ends a and C and the waveguide ends d are optically coupled. Regarding this optical switch 12K, for example, pplia4 Ph
ysics Letter Volume 27, No. 4 1975,
GaAa electro-optic direct
tional-couplerswitch.

FIG. 5 shows a configuration example in which the optical switch 12 is realized by a 5×3 type voltage-controlled optical directional coupler. Three optical waveguides 30 and 31 with equal optical characteristics are disposed on the electro-optic crystal substrate 20.
．． 32 are formed and control electrodes 33 .32 on these waveguides are formed.
The control voltage of the optical switch switching control signal terminal 13 is applied to 34 and 35. In this case as well, by applying an appropriate control signal voltage to the terminal 13 based on the same principle as in the case of FIG. 5, the four types of optical coupling states shown in FIGS. 6A to 6D can be realized. 1. For a detailed description of this optical switch, see, for example, ppl iθdOpt
ies Volume 17, No. 8 (April 15), 1978 0p
tical wave-guide 5w1tch
(3X 5) for an optical sw
It is shown in itching@yat@m.

By associating the waveguide ends a and bO in FIG. 3 or FIG. 5 with the terminals T and RlPK in FIG. You can change the reception time zone. In this case, the switch in FIG. 5 uses the combined states C and D in FIG. 6.

In addition to this, there are several ways to combine the terminals, and the present invention can also be implemented using these.

This enables bidirectional optical transmission in which transmission and reception are controlled in a time-division manner using one square transmission optical fiber.

The optical transmission signal generating section 9 in FIG. 2 can be constructed using a semiconductor laser or a light emitting diode, and the optical reception signal detecting section can be constructed using a photodiode, an avalanche photodiode, or the like. Furthermore, by using an optical integrated circuit in which the optical transmission signal generation section 9, the optical reception signal detection section 10, and the optical switch 12 are configured on the same substrate, the connecting optical fiber 11 is no longer necessary, and the device can be configured simply. Gadekuraru.

Now, considering the operating cycle of the optical switch 12, that is, the transmission/reception switching cycle, when the transmitted signal is an 8-bit POM signal (64 kb/s') encoded with audio, the transmission/reception switching is performed every 16 samplings. What you do is appropriate. In this case, the operation period Fi is 2 milliseconds. When the transmission path is short, the delay of the transmission path is small, so this operation synchronization is further shortened so that every sampling, that is, α1
It can also be every 25 milliseconds. Also, the upper limit of this cycle is approximately 20
It can be set to 0 milliseconds. If the signal to be transmitted is other than an audio signal, the range of this period may be further expanded.

As explained above, according to the present invention, 5. an optical switch having bidirectional passage characteristics is used for time division control of the transmission direction,
Bidirectional transmission is possible using an optical fiber as a transmission line.This device eliminates the need for impedance matching that depends on the length of the transmission path, and due to the low crosstalk and low loss characteristics of optical fiber, expensive bidirectional amplifiers are not required. This has the advantage that long-distance transmission is possible without using.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of a conventional time-division direction control type transmission system direction control section. FIG. 2 is a block diagram of an apparatus according to an embodiment of the present invention. FIG. 3 is a diagram showing an example of the configuration of an optical switch. FIG. 4 is an explanatory diagram of the operation. FIG. 5 is a diagram showing another configuration example of an optical switch. FIG. 6 is an explanatory diagram of the operation. 1... Speed converter, 2... Transmission signal line, 2'...
Transmission information line, 3... Reception signal line, 3' - Reception information line, 4... High speed switch, 5... Transmission/reception switching control signal terminal, 6... Amplifier, 7... Matching box. 8... Two-wire cable, 9... Optical transmission signal generator, 10-- Optical reception signal detector, 11-- Optical fiber for connection, 12-- Optical switch, 13--i switch switching control signal Terminal, 14-
- Transmission optical fiber, 15... Opposite device. Hikari 1'mouth" M 2 picture rough 3 mouth (-1, --J 3 兇 5 mouth child 6 mouth

Claims (2)

[Claims] (1) A time-division direction configured to time-divisionally switch signals on one transmission line to a transmission signal line and a reception signal line by a high-speed switch, and perform bidirectional communication using the transmission line. In the control optical transmission device, the high-speed switch is an optical switch whose optical path is switched by an applied electrical control signal, the transmission path is an optical fiber, and the common terminal of the optical switch is connected to the optical fiber. Time-division direction control optical transmission characterized in that an optical transmission signal generator and an optical reception signal detector are connected to two terminals to which one end is connected and the common terminal of the optical switch is alternately connected. Device. (2) The operating cycle of the optical switch is α1 milliseconds to 2 milliseconds
The time-division direction control optical transmission device according to claim 1, wherein the time-division direction control optical transmission device is in the range of 00 milliseconds.