JPS6130139A - Optical transmission system - Google Patents

Abstract

PURPOSE:To perform effectively the video distributing service and the bidirectional data transmission service to multiplex video channels by sharing an optical transmitter in a center station among n-number of subscriber's terminals. CONSTITUTION:An optical transmitter 3 and an optical receiver 4 in a center station 1 of an optical transmission system are coupled to (1Xn)-number of star couplers 7 through an optical filter 5, and #1-#n subscriber's terminals 2 are connected to output terminals of these couplers 7. The optical signal having a wavelength lambda1 from the optical transmitter 3 in the center station 1 is distributed to ports of couplers 7 and is supplied to #1-#n terminals 2 by optical fiber cables 6 and is applied to the optical receiver 5 through the optical filter 5. The optical signal having a wavelength lambda2 from the optical transmitter 3 in the terminal 2 is applied to the coupler 7 in the center station 1 through the optical filter 5 in the terminal 2 and the cable 6 and is applied to the optical receiver 4. Thus, the video distributing service and the bidirectional data transmission service are performed effectively to multiplex video channels.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical transmission system suitable for providing a video distribution service and a low-speed bidirectional data transmission service to a public communication network for general subscribers. .

[Conventional technology]

A communication network that provides services to general subscribers is a star-shaped communication network consisting of one center station and a large number of n subscriber terminals. The most basic communication services provided by this communication network are video distribution service and several Kb/s to several tens of Kb/s.
This is a two-way data transmission service of about 1/s. Although these services are multifunctional by taking advantage of the excellent features of optical transmission systems, severe economic efficiency is required in order to apply them to general subscribers.

To realize the above services, it is necessary to distribute video signals from the center station to each subscriber and at the same time establish a bidirectional digital transmission path between the center station and each subscriber. There are two ways to enable bidirectional communication using optical transmission methods: (1) providing two transmission lines, one for upstream and one for downstream, and (2) applying wavelength multiplexing technology. (2) is more economical because optical cables are expensive.

The most basic method of performing bidirectional communication between one center station and n subscriber terminals by applying wavelength multiplexing technology is as shown in FIG. 4, in which an optical transceiver 1. 2 and an optical filter 5 to perform bidirectional communication. According to this system, full-duplex communication is possible between the center station and each subscriber, and there is no limit to the number n that can be accommodated.

[Problem that the invention seeks to solve]

However, since a pair of optical transceivers are provided for each subscriber line on the center station side, there is a drawback that the cost becomes very high.

The object of the present invention is to eliminate the above-mentioned drawbacks and to economically provide a video distribution service and a two-way data transmission service.

[Means for Solving the Problems] The present invention provides a communication network that provides a video distribution service and a two-way data transmission service between one center station and a large number n subscriber terminals. , the center station and the n subscriber terminals include a pair of optical transceivers, and a pair of optical transceivers placed between the optical transceivers and the transmission line to separate upstream optical signals and downstream optical signals having different wavelengths. The center station further includes a 1×n star coupler connected to the optical filter and accommodating the n subscriber terminals via an optical cable, and the center station is equipped with The vessel is n
It is characterized by being shared by multiple subscriber terminals.

The optical transmission system of the present invention is characterized in that the optical transceiver of the center station is shared by n subscriber terminals. Therefore n
For bidirectional data transmission to individual subscriber terminals, optical transceivers are shared by frequency division or time division.

[Effect]

In a communication network with one center station and n subscriber terminals, the present invention aims to improve the economic efficiency of the system by connecting optical transceivers, etc. of the center station to n subscribers as described above. This means that both terminals can be shared. This is possible because the transmitted signal has the following characteristics.

(1) In the downlink from the center station to each subscriber, the video signal, which is a broadband signal, is the same for each subscriber, so one optical transmitter is placed at the center station, and passive components Suitable for branching.

(2) A pair of optical transceivers are placed in the center office, and the low-speed data signals are used by n subscriber terminals in a time-sharing manner.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention. An optical transmitter 3 and an optical receiver 4 in the center station 1 are coupled to an lXn star coupler 7 via an optical filter 5.
Each output of this star coupler 7 is connected to subscriber terminals #1 to #n, respectively.

In FIG. 1, an optical signal with a wavelength λ1 transmitted from an optical transmitter 3 of a center station 1 passes through an optical filter 5 and is distributed to n (#1 to #n) boats at a star bluff.
Each subscriber i (i=9
1 to #n), and is supplied to the optical receiver 4 by the optical filter 5 on the subscriber side. Conversely, each subscriber i (i=#
1 to #n) are multiplexed in the star bluff, passed through the optical filter 5, and supplied to the optical receiver 4 of the center station I.

FIG. 2 is an example of the frequency arrangement of the downlink signal when the video signal is of m channels in the above embodiment. FIG. 3 shows an example of the arrangement of the n time slots (#1 to #n) when the optical transceiver of the center station 1 is shared in a time-division manner for bidirectional data transmission.

〔Effect of the invention〕

As explained above, according to the optical transmission system of the present invention, since the optical transceiver of the center station is shared by n subscriber terminals, video distribution services and bidirectional data transmission services can be provided economically. A communication network can be configured. Furthermore, the services considered in the present invention are basic services such as cable television (CATV), which are expected to develop in the future, and are expected to have the effect of making it possible to increase the number of video channels by utilizing the broadband nature of optical cables. It will be done.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention. Figure 2 shows the side entrance of the m-channel video signal arrangement. FIG. 3 is a time slot diagram of (#1 to #n) time division signals. FIG. 4 is a block diagram of a conventional device. 1... Center station, 2... Subscriber terminal, 3... Optical transmitter (E'10), 4... Optical receiver (0/E),
5... Optical filter, 6... Optical fiber cable, 7
... lxH star coupler.

Claims (1)

[Claims] (1) In a communication network that provides video distribution services and bidirectional data transmission services between one center station and a number of n subscriber terminals, the center station and the n subscriber terminals , a pair of optical transceivers, and an optical filter placed between the optical transceiver and the transmission line to separate uplink optical signals and downlink optical signals of different wavelengths, and the center station includes: a pair of optical filters; An optical transmission system comprising: a 1×n star coupler which is connected to the n subscriber terminals via an optical cable and is shared by the n subscriber terminals.