JPS6276331A - Two-way optical fiber communication system - Google Patents

Abstract

PURPOSE:To avoid the transmission level of an optical signal of a center equipment from being increased as required or over by using a light-receiving level at each terminal equipment so as to control an optical signal level sent from the center equipment. CONSTITUTION:A video selection signal given to the input interface section 21 of a subscriber terminal equipment 2a is converted into an optical signal by a light emitting section 23 and the result is sent to a transmitter-receiver 1a. The multiplex section 22 multiplexes the video selection signal and light- receiving level information, the light emitting section 23 converts the result into an optical signal and the result is sent to a central station side. The light- receiving section 14 of the transmitter-receiver 1a of the central station 1 converts the signal into an electric signal, and the light emission control section 17 of a separation section 15 controls a light emitting drive section 12 depending on the quantity of the video selection signal and the light-receiving level information and the light output level of the light emitting section 13 is lowered to a near distance subscriber whose transmission distance is short. Thus, the light- receiving level of each subscriber terminal equipment is controlled to a nearly constant value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a bidirectional optical fiber communication system that performs bidirectional communication between a center device and a plurality of terminal devices via an optical fiber. In particular, the present invention relates to a two-way optical fiber communication system in which the level of an optical signal sent from a center device can be automatically controlled in accordance with the distance from the terminal device.

〔overview〕

The present invention provides a two-way optical fiber communication system that performs two-way communication between a center device and a plurality of terminal devices via an optical fiber. and a means for transmitting this received light level information to a center device, and the center device includes a means for automatically controlling the optical signal output level based on the bell information transmitted by the terminal device. This allows the optical signal level sent from the center device to be automatically controlled in accordance with the distance from the terminal device.

[Conventional technology]

Common forms of bidirectional fiber optic communication systems include C
Like an ATV or telephone subscriber line, a center device and a plurality of terminal devices perform two-way communication via optical fibers. In such a system, it is common to install a transmitting/receiving device compatible with the terminal device in the center device, and to connect each transmitting/receiving device and the terminal device with a dedicated optical fiber. In this type of system, each terminal device is generally scattered in various locations, so the transmission distance between the center device and each terminal device, and therefore the transmission loss, differ from each other.

Conventionally, in order to absorb the above-mentioned variations in transmission loss, optical signals at a standard constant level were sent from the transmitting sides of both the center equipment and the terminal equipment, and automatic gain control was applied to the receiving sides of both the center equipment and the terminal equipment. Adds functionality.

[Problems to be Solved by the Invention] However, in such conventional bidirectional optical fiber communication systems, even if the distance between the center device and the terminal device is shorter than the standard distance, both the center device and the terminal device are connected more than necessary. This results in the transmission of an optical signal with a high output level, which poses a problem in that there is a large waste of power in terms of power consumption and the life of the light emitting element.

The present invention solves these conventional problems,
It is an object of the present invention to provide a bidirectional optical fiber communication system in which the level of an optical signal sent from a center device can be automatically controlled to an optimum level in accordance with the distance to a terminal device.

[Means for solving problems]

The present invention includes one center device and a plurality of terminal devices each connected to the center device via individual optical fibers, and the center device has a plurality of terminal devices connected to each of the optical fibers corresponding to each terminal device. In a two-way optical fiber communication system including a transmitting/receiving device that transmits and receives optical signals, the terminal device includes a means for detecting a received light level from the center device, and a means for detecting the received light level information detected by this means. means for multiplexing and transmitting a signal to be transmitted to a center device, and the transmitting/receiving device of the center device includes means for automatically controlling an optical signal output level based on the received light level information sent by the terminal device. It is characterized by including.

[For production]

The present invention detects the received light level of an optical signal from a center device in a terminal device, sends this received light level information to the center device, and the center device automatically controls the optical signal output level based on this received light level information. , the level of the optical signal sent from the center device can be automatically controlled to the optimum level in accordance with the distance to the terminal device.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In this embodiment, a selective video signal transmission system such as CATV will be described.

FIG. 2 is a block diagram showing an example of an optical fiber communication system to which the bidirectional optical fiber communication system of the present invention is applied.

This system includes a central office 1 as a center device, and subscriber terminal devices 2a, 2b, 2c, ..., 2 as a plurality of terminal devices.
n, and optical fibers 3a, 3b, 3c, . . . -13n having different lengths that interconnect these fibers. The central station I includes a headend IA that supplies video signals of multiple channels, and subscriber terminal devices 2a, 2b, 2.
Transmitting/receiving device 1a corresponding to each of c, -12n
, 1b, 1c1, -., In.

In FIG. 1, a transmitting/receiving device 1a of a central office 1 and a subscriber terminal device 2a are connected by an optical fiber 3a of a suitable length.

The transmitting/receiving device 1a includes a video signal selection unit 1) to which a video signal is connected to one input, a light emission drive unit 12 to which the output of the video signal selection unit 1) is connected to one input, and an output of the light emission drive unit 12. Light emitting unit 13 for input, light receiving unit 1 for receiving optical signals
4. A separation unit 15 that separates the output of the light receiving unit 14 into a video selection signal and light reception level information, a video signal selection control whose input is this video selection signal and whose output is connected to the other input of the video signal selection unit 1). section 16, a light emission control section 17 whose input is received light level information and whose output is connected to the other input of the light emission drive section 12, a light emission section 13, an optical fiber 3a, and an optical fiber 3;
It is composed of an optical multiplexer/demultiplexer 18 that connects a and the light receiving section 14.

The subscriber terminal device 2a includes an input interface section 21 that inputs a signal for selecting a desired video, a multiplexing section 22 that receives the output of the input interface section 21 as one input, and a light emitting section that receives the output of the multiplexing section 22 as an input. 23. A light receiving section 24 that receives an optical signal, an intensifying ψM section 25 that receives the output of one of the light receiving sections 24 as an input, a received light level detecting section 26 that receives the output of the other, and a multiplexing section for the outputs of the received light level detecting section 26. 22, the interface section 27, the light emitting section 23 and the optical fiber 3
a and an optical multiplexer/demultiplexer 28 that connects the optical fiber 3a and the light receiving section 24.

A video selection signal is sent to the subscriber terminal device 2a via the input interface section 21, converted into an optical signal by the light emitting section 23, and sent to the transmitting/receiving device 1a corresponding to each subscriber terminal device via the optical fiber 3a.

This signal is reconverted into an electrical signal by the light receiving section 14 and sent to the video signal selection control section 16, which controls the video signal selection section 1) to select the video signal, thereby selecting the video signal desired by the subscriber. The light output level of the light emitting part 13 of the transmitting/receiving device 1a, which is transmitted via the light emitting drive part 12 and the light emitting part 13 and received by the subscriber/terminal device 2a, is the same as that of the light receiving part 1.
If there is no input in 4, the initial maximum value is set.

In the subscriber terminal device 2a, the received light level detection unit 26 detects
The level of light received by the light receiving section 24 is detected, and this received light level information is sent to the multiplexing section 22 via the interface section 27. The multiplexing section 22 multiplexes the video selection signal and the light reception level information, and the light emitting section 23 converts the signal into an optical signal and sends it to the central office side. In the transmitting/receiving device 1a of the central station 1, the light receiving section 14 converts the signal into an electrical signal, and the separating section 15 separates it into a video selection signal and a received light level information signal. The light emission control section 17 controls the light emission driving section 12 according to the magnitude of the received light level information,
For short distance subscribers whose transmission distance is short, the light output level of the light emitting unit 13 is lowered, and the light reception level at each subscriber terminal gW is lowered to the set value.

Therefore, the light receiving level of a subscriber terminal device having an input having a level higher than the preset light receiving level is automatically lowered, and the light receiving level of each subscriber terminal device is controlled to a substantially constant value.

〔Effect of the invention〕

As explained above, the present invention controls the level of the optical signal sent out from the center device based on the light reception level at each terminal device, so that the center device can There is no need to increase the transmission level of the optical signal more than necessary, and there is an effect that the life of the element of the light emitting section can be extended and power consumption can be reduced. Additionally, the signal-to-noise ratio is improved in the case of remote locations.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention. FIG. 2 is a block diagram showing an example of an optical fiber communication system to which the bidirectional optical fiber communication system of the present invention is applied. 1...Central office, IA...Head end, 1c%il
), 1c, -1ln=-transceiver, 2a, 2b, 2c
, -22n-Subscriber terminals, 3a, 3b, 3c. ..., 3n... optical fiber, 1)... video signal selection section, 12... light emission drive section, 13... light emission section, 14
... Light receiving section, 15... Separation section, 16... Video signal selection control section, 17... Light emission control section, 18... Optical multiplexer/demultiplexer, 21... Input interface section, 22. ...multiplexing section, 23...light emitting section, 24...light receiving section, 25...
- Amplification section, 26... Light reception level detection section, 27... Interface section, 28... Optical multiplexer/demultiplexer.

Claims (1)

[Claims] (1) Equipped with one center device and a plurality of terminal devices each connected to this center device via individual optical fibers, and the center device has a plurality of terminal devices connected to each of the above optical fibers corresponding to each terminal device. In a two-way optical fiber communication system including a transmitting/receiving device for transmitting and receiving optical signals, the terminal device includes a means for detecting a received light level from the center device, and a means for transmitting the received light level information detected by this means to the center device. the transmitter/receiver of the center device includes means for automatically controlling the optical signal output level based on the received light level information sent by the terminal device; A bidirectional optical fiber communication system featuring: