JPH01202941A - Optical transmission/reception system - Google Patents

Abstract

PURPOSE:To attain the detection of collision with high accuracy by converting a prescribed collision detection pattern into a 2nd wavelength optical signal different from a 1st signal during transmission period of the optical signal of the 1st wavelength, synthesizing the 2nd signal with the optical signal of the 1st wavelength and sending the result to an optical star coupler. CONSTITUTION:When a transmission data SD is sent from a terminal equipment while no data is received, the data is led to a data optical transmitter 11, where the signal is converted into an opticalsignal with a wavelength lambda1. When the transmission data SD is given in this case, a collision detection pattern AP is generated consecutively from the pattern generator 13 during the input period. Then the pattern AP is converted into the optical signal with a wavelength lambda2 different from the wavelength lambda1 by the collision detection signal optical transmitter 1. When the optical signal comes from the optical star coupler, the signal is branched into the optical signals with wavelengths lambda1, lambda2, and the optical signal with the wavelength lambda2 is led to the collision detection optical receiver 24. Then the collision detection optical receiver 24 discriminates the presence of the code rule violation from the optical signal with the wavelength lambda2 and the result of discrimination is sent to the terminal equipment as a collision detection signal CD.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an optical transmission/reception system applied to an optical transmission system constituting, for example, an optical LAN (local area network).

(Prior Art) In recent years, optical LANs have been put into practical use in various fields by taking advantage of the broadband properties and anti-electromagnetic interference properties of optical fibers used as optical transmission lines.

Among them, optical LANs using optical star couplers as center nodes are attracting attention as small to medium-sized LANs because each terminal device is distributed and the transmission control procedure is simple. FIG. 2 shows an example of the configuration of this type of system, in which an optical star coupler 1 is used as a center node, and an optical transceiver 3 is connected to each input/output port of the optical star coupler 1 via an optical transmission line 2 made of an optical fiber. A terminal device 4 is connected to each optical transceiver 3.

In addition, this type of LAN generally uses CSMA/CD (Carrier Sensing System) as its transmission control method.
eMultiple Access/Co11isi
on Detection) method. In this C8MAZCD method, each optical transceiver monitors the arrival of optical signals during standby, and when transmission data is sent from a terminal device without an optical signal arriving from anywhere, it converts this transmission data into an optical signal. and sends it out toward the optical star coupler 1. While the optical signal is being received, even if the terminal device 4 sends out transmission data, the transmission data is not transmitted. - When an optical signal is sent from another optical transceiver 3 via the destination star coupler 1, the optical transceiver 3 receives this optical signal, reproduces the data, and transfers it to the terminal device 4. In addition, if multiple optical transceivers transmit simultaneously, a collision of optical signals will occur on the destination star coupler, so when each optical transceiver receives an optical signal, it detects the presence or absence of a collision from its reception output, and when a collision is detected. The system notifies the terminal device of this fact and causes it to stop transmitting data.

By the way, in order to operate the system efficiently, there are two requirements: to accurately detect the collision of the optical signals. but,
It is generally impossible to obtain a high collision detection rate if data consisting of an NRZ code sent from a terminal device is directly converted into an optical signal and sent out. Therefore, in the past, the data to be transmitted was converted, for example, by double Manchester, and then sent.
Collision detection is performed by performing partial response conversion on this optical signal on the receiving side and then performing binary identification. In this way, if a collision of optical signals occurs in the optical star coupler, the identification code will change even if the collision signal is at a low level, and this will cause a code rule violation (CRV). By determining this, the occurrence of a collision can be detected with high accuracy.

However, in such a conventional system, data is subjected to double Manchester transformation, so the transmission speed of the optical signal is four times that of the data sent from the terminal device. Therefore, the upper limit of the data transmission speed must be limited to 1/4 or less of the maximum speed of optical signals that can be transmitted and received by the optical transceiver, and as a result, the data transmission speed cannot be further increased. There wasn't.

(Problems to be Solved by the Invention) As described above, the conventional optical transmission and reception method has the problem that the data transmission speed cannot be increased because the transmission data is sent after double Manchester conversion. ,
The present invention focuses on this point and attempts to provide an optical transmission/reception method that can increase data transmission speed while maintaining high collision detection accuracy.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides that, in each optical transceiver, when transmission data is sent from a terminal device, this data is converted into an optical signal of a first wavelength and transmitted as an optical signal. Along with sending it to the star coupler,
During the transmission period of this optical signal, a predetermined collision detection pattern is converted into an optical signal of a second wavelength different from the first wavelength, and then multiplexed with the optical signal of the first wavelength and sent to the optical star coupler. When an optical signal arrives from the optical star coupler, the optical signal is demultiplexed into an optical signal of the first wavelength and an optical signal of the second wavelength. In addition to reproducing data from the signal, collision detection is performed from the optical signal of the second wavelength.

(Function) As a result, collision detection is performed using the collision detection pattern regardless of the data, so code conversion such as double Manchester transformation, which is necessary for highly accurate collision detection, must be performed on the data. It is possible to convert it into an optical signal and send it out without any modification. Therefore, it is possible to increase the data transmission speed accordingly.

(Embodiment) FIG. 1 shows the configuration of an optical transceiver to which an optical transmission/reception system is applied in an embodiment of the present invention. The transmission system of this optical transceiver includes a data optical transmitter 11 and a collision detection signal optical transmitter 12, and further transmits a predetermined collision detection pattern AP in synchronization with the input timing of transmission data SD from the terminal device. It is equipped with a pattern generator 13 that generates patterns. First of all, the data optical transmitter 11
converts transmission data SD sent from a terminal device (not shown) into an optical signal of wavelength λ1 and outputs the optical signal.

The collision detection signal optical transmitter 12 converts the collision detection pattern generated by the pattern generator 13 into an optical signal having a wavelength λ2 different from the data wavelength λ1, and outputs the optical signal. The optical signal with the wavelength λ1 and the optical signal with the wavelength λ2 output from these optical transmitters 11 and 12 are combined by the optical multiplexer 14 and then sent to the output optical connector 15.
The signal is sent out to the transmission optical transmission line via.

The receiving system of the first transceiver introduces an optical signal sent from an optical star coupler (not shown) through an optical input connector 21 and separates it into an optical signal with a wavelength λ1 and an optical signal with a wavelength λ2. 22, a data optical receiver 23, and a collision detection optical receiver 24. Of these, the data optical receiver 23 receives the wavelength λ supplied from the optical demultiplexer 22.
The data RD is reproduced from the optical signal of 1, and the reproduced data RD is output to the terminal device. Further, the collision detection optical receiver 24 receives the optical signal of wavelength λ2 supplied from the optical demultiplexer 22 and reproduces the collision detection pattern AP. This collision detection pattern AP is subjected to partial response conversion, for example, and then subjected to binary identification to determine whether or not there is a violation of the coding rule, and the determination output is outputted to the terminal device as a collision detection signal CD.

With such a configuration, if the transmission data SD is sent from the terminal device while data is not being received, this transmission data S
D is guided to the data optical transmitter 11, where it is converted into an optical signal of wavelength λl. Also, at this time, the above transmission data S
When D is input, the pattern generator 13 continuously generates the collision detection pattern AP during this input period. This collision detection pattern AP is converted by the collision detection signal optical transmitter 1 into an optical signal having a wavelength λ2 different from the data wavelength λl. The optical signal with the wavelength λl and the optical signal with the wavelength λ2 output from these optical transmitters 11 and 12 are combined by the optical multiplexer 14 and then sent to the transmission optical transmission line via the optical output connector 15. be done.

When an optical signal arrives from the first star coupler, this optical signal is guided to the optical demultiplexer 22 via the optical input connector 21, where it is demultiplexed into an optical signal with wavelength λ1 and an optical signal with wavelength λ2. Ru. Of these, the optical signal with wavelength λ1 is guided to a data optical receiver 23, and the optical signal with wavelength λ2 is guided to a collision detection optical receiver 24. As a result, the data optical receiver 23 reproduces data from the signal of wavelength λ1, and this received data RD is transferred to the terminal device. Further, the collision detection optical receiver 24 determines whether or not there is a violation of the coding rule from the optical signal of the wavelength λ2, and outputs the determination result to the terminal device as a collision detection signal CD.

In this way, the method of this embodiment generates a collision detection pattern AP different from the data SD during the transmission period of the transmission data SD, and uses this collision detection pattern AP as the transmission data SD.
The collision detection pattern is simultaneously transmitted at a wavelength different from that of the collision detection pattern, and the reception side detects the occurrence of a collision from the collision detection pattern. Therefore, double Manchester transformation and the like for highly accurate collision detection need only be performed on the collision detection pattern AP, and the data can be transmitted as it is, for example, converted into an optical signal in the NRZ code. Therefore, data can be freely transmitted, thereby increasing the transmission speed. Regarding collision detection, by transmitting the collision detection pattern in a code structure that allows highly accurate collision detection, highly accurate collision detection can be performed without any change from the conventional technology.

It should be noted that the present invention is not limited to the above embodiments, and for example, the values of the data wavelength and collision detection wavelength, the configuration of the collision detection pattern, the collision detection method, the circuit configuration of the optical transceiver, etc. Various modifications can be made without departing from the spirit of the invention.

[Effects of the Invention] As detailed above, according to the present invention, in each optical transceiver, when transmission data is sent from a terminal device,
This data is converted into an optical signal of a first wavelength and sent to the optical star coupler, and during the sending period of this optical signal, a predetermined collision detection pattern is converted to an optical signal of a second wavelength different from the first wavelength.
After converting the optical signal into an optical signal having a wavelength of The optical signal is split into an optical signal with a wavelength of Accordingly, it is possible to provide an optical transmission/reception method that can perform collision detection with high accuracy and can increase data transmission speed.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing the configuration of an optical transceiver to which an optical transmission/reception system is applied in one embodiment of the present invention, and FIG.
The figure is a diagram showing an example of the configuration of an optical transmission system using an optical star coupler. 1... Optical star coupler, 2... Optical transmission line, 3...
Optical transceiver, 4... Terminal device, 11... Optical transmitter for data, 12... Optical transmitter for collision detection signal, 13
... pattern generator for generating patterns for collision detection, 14 ... optical multiplexer, 15 ... optical output connector,
21... Optical input connector, 22... Optical demultiplexer, 23
... Optical receiver for data, 24... Optical receiver for collision detection, SD... Transmission data, RD... Reception data, A
P: Collision detection pattern, CD: Collision detection signal. Applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] In an optical transmission system in which an optical star coupler is used as a center node and a plurality of terminal devices are connected to the optical star coupler through optical transmission lines and optical transceivers, each optical transceiver receives transmission data from the terminal device. In this case, this data is converted into an optical signal of a first wavelength and sent to the optical star coupler, and during the sending period of this optical signal, a predetermined collision detection pattern is converted to an optical signal of a second wavelength different from the first wavelength. After converting the optical signal into an optical signal of the first wavelength, the optical signal is combined with the optical signal of the first wavelength and sent to the optical star coupler, and when the optical signal arrives from the optical star coupler, this optical signal is converted into the optical signal of the first wavelength. An optical transmission/reception system characterized in that data is recovered from the optical signal of the first wavelength by demultiplexing the optical signal of the first wavelength and the optical signal of the second wavelength, and collision detection is performed from the optical signal of the second wavelength.