JPH01126027A - Optical remote multiplex transmission system for subscriber line - Google Patents

Abstract

PURPOSE:To prevent the deterioration in S/N and to eliminate the need for synchronization establishment time in a remote equipment by assigning different n-set of wavelength to each subscriber transmission optical signal. CONSTITUTION:Optical transmission circuits 24-1-24-n of wavelengths lambda21-lambda2n assigned to each subscriber are provided respectively to subscriber equipments 51-5n and the optical signal with a wavelength assigned to each subscriber from the optical transmission circuits 24-1-24-n is sent to a remote equipment 3. The remote equipment 3 synthesizes optical signals sent from each subscriber by an n:1 optical star coupler 26 and sends the result to an intra-office equipment 1 as it is. The equipment 1 uses an optical demultiplexer 9 to multiplex the subscriber transmission optical signal sent from the remote equipment 3 into each subscriber transmission optical signal and the signal is received by reception circuits 27-1-27-n corresponding respectively to each subscriber and the optical signal is converted into an electric signal. Moreover, the optical signal sent from the equipment 1 to the subscriber is processed similarly as a conventional system.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a subscriber line optical remote multiplex transmission system for transmitting digital signals between a station and an optical subscriber via a remote device.

[Conventional technology]

In recent years, 15DN (integrated service/
Digital network) plans are being actively considered in countries around the world.

FIG. 2 is an example (Japanese Patent Laid-Open No. 61-45699).

That is, when the remote device 3 demultiplexes the optical time-division multiplexed signal of wavelength λ1 transmitted from the in-office bag fil as an optical signal and supplies it to each subscriber device 51 to 5n, the remote device 3 1 converts the optical time division multiplexed signal from 1 into an electrical signal, performs frame synchronization with the converted output, controls the optical switch 12 for optical demultiplexing, and distributes to each subscriber device 51 to 5n. Conversely, the transmission signal from each subscriber device 51 to 5□ to the in-office device 1 is spectrum spread using a PN pattern (PNI to PNI,) unique to each subscriber, and then converted into an optical signal of wavelength λ2, and then transmitted remotely. The n-to-1 star coupler 26 of the device 3 combines the optical signals from each subscriber device 51 to 5□ and sends it to the in-office device 1, and the in-office device 1 converts the optical signal (wavelength λ2) into an electrical signal. , is a method of spread spectrum demodulation.

[Problem that the invention seeks to solve]

In the above-mentioned conventional technology shown in FIG. 2, it is extremely difficult to fix all the optical signals transmitted from each subscriber to the same wavelength λ2 and keep them stable, and each optical signal may fluctuate independently. big.

If it becomes difficult to keep the transmission wavelengths of individual subscriber devices at the same value and stable over a long period of time, it will take a long time to establish synchronization of the codes of the spread spectrum demodulator in the station equipment 1. Problems arise, such as deterioration of transmission quality due to deterioration of signal-to-noise ratio S/N. Furthermore, if the wavelength variation range is large, communication may become impossible due to loss of synchronization.

An object of the present invention is to provide a method for solving the above-mentioned conventional problems.

[Means for solving problems]

The above object is achieved by assigning n different wavelengths λ21 to λ2n to each subscriber's transmitted optical signal. That is, each subscriber device is equipped with an optical transmission circuit for the wavelengths λ21 to λ2□ assigned to each subscriber, and the wavelength (any one among λz-λ2n) assigned to each subscriber from the optical transmission circuit is provided. 1 wavelength) to a remote device. At the remote device, the optical signals sent from each subscriber are multiplexed by an n-to-1 optical star coupler and sent as is to the in-office device.In the in-office device, the optical signals sent from each subscriber are multiplexed and sent to the subscriber transmission light sent from the remote device. The signal is demultiplexed into optical signals transmitted by each subscriber using an optical demultiplexer, and the optical signal is converted into an electrical signal by a receiving circuit corresponding to each subscriber.

Since the optical signal sent from the in-office equipment to the subscriber can be done using conventional technology, the description thereof will be omitted.

[Effect]

In the method of the present invention, each subscriber's transmitted optical signal is divided into separate allocated wavelengths and sent to a remote device, and the star coupler of the remote device multiplexes and wavelength-multiplexes the optical signals to the local device. The signal is sent to the station, and is demultiplexed by a demultiplexer in the in-office equipment into optical signals transmitted by each subscriber and converted into electrical signals. Therefore, problems caused by wavelength non-uniformity and instability of each subscriber's transmitter, which were problems with conventional spread spectrum transmission systems, do not occur (such as taking a long time to establish synchronization, causing S/N deterioration, etc.). Costs can be reduced because there is no need for selection of light sources to ensure the wavelength identity of the light sources required for each subscriber device, an isolator for the optical signal transmitted by each subscriber provided in the remote device, or a spread spectrum modulation/demodulation device.

〔Example〕

An embodiment of the present invention shown in FIG. 1 will be described below. As in the conventional example, one in-office device 1 and remote device 3 are connected by one optical fiber transmission line 2, and n subscriber devices 5-1 to 5-0 are connected to each remote device 3. They are connected via optical fiber transmission lines 4-z to 4-. There are 5 subscriber devices
It has the same configuration as the devices shown in -1 to 5-l.

First, signal transmission sent from the in-office device 1 to each subscriber device 5-1 to 5-9 will be explained. An optical signal having a wavelength λ1 transmitted from the optical transmission circuit 8 is sent to the remote device 3 via a demultiplexer 9° and an optical fiber transmission line 2. The wavelength λ1 sent from the local device 1 by the demultiplexer 10 in the remote device 3
The multiplexed signal is input to the time division optical switch section 31.

This time-division optical switch section 31 has a wavelength λ as in the conventional example.
The receiving circuit converts and demodulates the optical signal of 1 into an electric signal, and from the demodulated output, a frame synchronization circuit extracts a synchronization signal for optical multiplexing and demultiplexing.The synchronization signal controls the time division optical switch drive control circuit. The input information signals INz to INn are sequentially demultiplexed and transmitted to the respective subscriber optical fibers 4-1 to 4-n by the time-division optical switches controlled in this manner.
The signal is sent to each subscriber device 5-1 to 5-n, and is converted and demodulated by an optical receiving circuit provided in each subscriber device 5-z to 5-n.

Next, signal transmission sent from each subscriber device 5-1 to 5-0 to the in-office device 1 will be explained. Each subscriber device i! 5
- The respective subscriber input information and information signals IN1' to Nn' are transmitted by the transmitting circuits 24-1 to 24-n whose oscillation optical signal wavelengths are the wavelengths λzl to λXn assigned to t to 5-0, respectively. The wavelengths are converted into corresponding wavelengths λ21 to λ2n, and connected to the respective demultiplexers 18-1 to 18-n and the subscriber optical fiber 4.
-1 to 4-0 to the remote device 3.

In the remote device 3, optical signals with wavelengths λ21 to λ2o are multiplexed by a 1:n optical star coupler 26 via corresponding demultiplexers 17-1 to 17-0, respectively. Here, as in the conventional example, the demultiplexers 17-1 to 17-n and the 1-to-n optical star coupler 26
It is not necessary to insert an isolator between the two. This is because each demultiplexer acts as a bandpass filter that only passes optical signals with wavelengths assigned to it, so optical signals with wavelengths other than those assigned to each demultiplexer are passed through the demultiplexer. One of the features of the system of the present invention is that the input information signals of other subscribers are not cut and leaked to each subscriber device. The multiplexed subscriber input information signals INI' to INn' are sent to the in-office equipment 1 through the optical fiber transmission line 2, and are separated into respective subscriber input information signals by the demultiplexer 9 in the in-office equipment 1. The signals are then converted into electrical signals and demodulated by optical receiving circuits 27z to 27n corresponding to each subscriber.

As described above, bidirectional transmission is performed between the station and the optical subscriber via the remote equipment.

Although the oscillation wavelength of a semiconductor laser can be selected and used as the light source transmitted from each subscriber device, it is also possible to cut out the optical signal of a light emitting diode, for example, a white light source, etc. with a filter and use it.

Here, the relationship between the wavelength λl of the optical signal sent from one station to the subscriber unit and the wavelengths λ21 to λtn of the optical signals sent from each subscriber unit to the station, and the configuration of the demultiplexer 9 of the in-office unit will be described. Third
Figures (a) and (b) show the wavelength λ considered to be applied in this example.
1 and the spectrum showing the relationship between λ21 and λ2o (c
) shows a schematic diagram of the configuration of the duplexer 9. Figure 3 (a), (
b) As can be seen from the diagram, the wavelengths λ21 to λ2 are different from the wavelength λ1.
Create a wavelength spectrum relationship that allows n to be treated as one group. From the above-mentioned spectral relationship, the configuration shown in (C) can be considered as the duplexer 9.

The optical time division multiplexed signal λ signal transmitted from the station is sent to the optical fiber transmission line 2 via the multiplexer/demultiplexer 33 which can be configured with a directional coupler, grating element, etc. Incoming subscriber input information optical signal λ2~λ2n
is sent to the duplexer 32.

The demultiplexer 32 is composed of a Matsuhatsu Enda interferometer and a tuner pull optical filter, whereby the wavelength-multiplexed and sent subscriber input information optical signals λ21 to λIn are demultiplexed into respective optical signals. Each receiving circuit 27z~27
．． sent to.

〔Effect of the invention〕

According to the present invention, the conventional technology is used as is for optical transmission from inside the station to inside each subscriber equipment, and when performing optical transmission from inside each subscriber equipment to inside the office, each wavelength corresponding to each subscriber equipment is used. Different optical signals are allocated and transmitted within the office using the optical fiber transmission line used in conventional technology, and then split into optical signals from each subscriber for bidirectional transmission.As a result,
There is no need for synchronization establishment time, and a high S/N ratio can be achieved.

Furthermore, as described in the embodiment (FIG. 1), the isolator in the remote device, which is required in the prior art, is not required, so cost can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a subscriber line optical remote multiplex transmission system according to an embodiment of the present invention, FIG. 2 is a schematic block diagram of a conventional subscriber line optical remote multiplex transmission system, and FIG. (b) is a wavelength spectrum 11 diagram of the dynamic input optical time division multiplexed signal and the subscriber input information optical signal, and (c) is a schematic block diagram of the configuration of the demultiplexer 9.
γゝ・I Agent Patent Attorney Katsuma Ogawa ゝ, -7 (-1)' Kaya 2

Claims (1)

[Claims] 1. An optical time division multiplexed signal of wavelength λ_1 is sent from the optical transmission circuit of the in-office device to a remote device, and the remote device distributes and transmits the optical time division multiplexed signal to each subscriber using a time division optical switch. The subscriber device receiving section converts the optical signal of wavelength λ_1 distributed from the remote device into an electrical signal, and conversely, each subscriber device transmitting section converts the optical signal of wavelength λ_1 distributed from the remote device into an electrical signal, and conversely, the optical signal of wavelength λ_1 assigned to each subscriber is converted into an electrical signal.
2_1 to λ_2_n to a remote device using optical signals;
In the remote equipment, the subscriber transmission signals of wavelengths λ_2_1 to λ_2_n are multiplexed by an n:1 star coupler and transmitted to the in-office equipment, and the in-office equipment demultiplexes the multiplexed subscriber transmission signals and sends them to each subscriber. A subscriber line optical remote multiplex transmission system characterized in that an assigned optical receiving circuit converts the signals transmitted by each subscriber into electrical signals and performs bidirectional transmission.