JPS6253032A - Optical fiber two-way transmission system - Google Patents

Abstract

PURPOSE:To decrease number of components by providing a light emitting element sending an optical signal to a transmission line and a photodetector receiving the optical signal from the transmission line to a master set and providing an element in common use for transmission/reception transmitting/ receiving the optical signal to/from the transmission line to a slave set. CONSTITUTION:The master set A and n-set of slave sets B1-Bn are coupled by one-core optical fiber F and a star coupler C. The master set A is provided with the light emitting element S, the photodetector R and a coupling mirror M coupling the light emitting element S and the photodetector R with the opti cal fiber F. The slave sets B1-Bn are provided respectively with an element SR in common use for transmission/reception. The optical signal sent from the light emitting element S of the master set A is received to the element SR of the slave sets B1-Bn via the optical fiber F and the star coupler C. Then the optical signal sent from the element SR of the slave sets B1-Bn is received by the photodetector R of the master set A.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention is utilized in optical fiber communications. The present invention is suitable for relatively simple optical communications such as local area networks of information processing devices.

〔overview〕

The present invention relates to a time-division switching type bidirectional transmission system in which a main device and a slave device are connected through a single optical fiber. By using a transmitting/receiving element without separately providing a light receiving element and a light receiving element, an economical system with high transmission efficiency is provided.

[Conventional technology]

In information processing devices, a simple communication method using optical fibers is used between a main device including, for example, a central processing unit and a slave device serving as an operation terminal.

If a two-core optical fiber is installed between the main device and the slave device, bidirectional communication is possible at the same time, but this method does not require question-and-answer type communication between the main device and the slave device. Since it is not always necessary to carry out bidirectional communication at the same time, a method is widely used in which a negative-core optical fiber is installed and transmission and reception are performed alternately by time-division switching control.

FIG. 3 is a block diagram of a conventional device. One main device A and n slave devices B, ~Bn are coupled by a -core optical fiber F and a star coupler C. The main device A and the slave devices B, -Bn each include a light emitting element S, a light receiving element R, and a coupling mirror M that couples the light emitting element S and the light receiving element R to an optical fiber F.

FIG. 4 is a block diagram of another conventional device. In this example, the optical fiber F and the star coupler C are similar to the example shown in FIG. is combined with

[Problem that the invention seeks to solve]

In the example shown in FIG. 3, the light emitting element and the light receiving element are provided in the main device A and the n slave devices 81 to Bn, respectively, so the number of parts is large and the cost is high. Furthermore, coupling with the optical fiber F using a coupling mirror requires mechanical precision and is expensive.

On the other hand, in the example shown in FIG. 4, the light emitting element and the light receiving element are not provided separately, and a transmitting/receiving element is used, so the number of components is small and the cost is low, but there is a drawback of poor communication efficiency. In other words, when a transmitting/receiving element is used, the luminous power cannot be obtained by using a dedicated light emitting element.
56) has a disadvantage that there is a wavelength shift between the emission spectrum and the maximum light-receiving sensitivity spectrum, resulting in poor efficiency.

The present invention improves this, and aims to provide a two-way communication system with high communication efficiency without increasing the number of parts.

[Means for solving problems]

In the present invention, one main device and a plurality of slave devices are connected by a transmission path including an optical fiber and a branching/coupling circuit,
The transmission path is such that the optical signal sent by the main device reaches all the slave devices, and one of the slave devices.

In an optical fiber bidirectional transmission system that includes means for time-divisionally switching transmission and reception, the optical signal to be transmitted is configured to reach at least the main device, and the main device includes a light emitting element that transmits the optical signal to the transmission path. and a light-receiving element that receives an optical signal from the transmission path, and the slave device includes a transmitting/receiving element that transmits and receives the optical signal to and from the transmission path.

The branch-coupling circuit can be a star coupler.

The light emission wavelength of the light emitting element of the main device approximates the wavelength of the maximum light receiving sensitivity of the light receiving element of the slave device, and the maximum light receiving sensitivity wavelength of the light receiving element of the main device approximates the light emission wavelength of the light emitting element of the slave device. Preferably, the characteristics are selected.

[Effect]

Since the main device is small in number, the overall number of parts will only increase at a small rate, even apart from the light-emitting element and the light-receiving element.Also, the light-emitting element in the main device has an emission spectrum that has the maximum light-receiving sensitivity of the transmitter-receiver element. Furthermore, the light-receiving element of the main device can be selected so that its maximum light-receiving sensitivity wavelength coincides with the emission spectrum of the non-transmitting/receiving element. That is, since the number of main devices is small, even if somewhat expensive elements are selected, the effect on the overall price is small.

〔Example〕

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention. One main device A and n slave devices B+xBn are connected to a -core optical fiber F.
and are coupled by a star coupler C. Star coupler C has n+1 terminals, and distributes an optical signal arriving at any one terminal to the other n terminals. The main device A includes a light emitting element S, a light receiving element R, and a coupling mirror M coupling the light emitting element S and the light receiving element R to an optical fiber F. The slave devices Bl mBn are each equipped with a transmitter/receiver element SR, and each of these is coupled to an optical fiber F.

Main device A is connected to a central processing unit (not shown), and slave device B
+ -Bn are each connected to a terminal device not shown in the figure.0 Communication is performed alternately between the main device A and the slave devices 81 to Bn in a time-sharing manner, and switching between transmission and reception is performed by the main device A. This is done under the control of a connected central processing unit.

In such a device, the optical signal transmitted by the light emitting element S of the main device A is received by the transmitting/receiving device SR of each of the slave devices B1 to Bn via the optical fiber F and the star force “Fuplar C”. , the optical signal transmitted by the transmitting/receiving element SR of each slave device B, -Bn is received by the light receiving element R of the main device A.

FIG. 2 is a diagram showing the wavelength characteristics of the transmitter/receiver element used in this example. In this figure, the horizontal axis represents the wavelength, and the vertical axis shows the normalized emission power spectrum (solid line) and photosensitivity spectrum (dashed line).In other words, the wavelength of the maximum spectrum of the emission power has the maximum photosensitivity. There is a difference from the wavelength.

However, in the device of the present invention, although the main device A is provided with the light emitting element S and the light receiving element R separately, the light emitting element S
The light-emitting element S and the light-receiving element R can be selected so that the maximum spectrum of the light-receiving element becomes the arrow S in FIG. 2, and the maximum sensitivity wavelength of the light-receiving element becomes the arrow R in FIG. Further, a laser diode with a large output light can be used as the light emitting element S, and a laser diode with high sensitivity can be used as the light receiving element R.

In the above example, the means for branching and coupling a plurality of optical fibers is a star coupler, but the present invention can be similarly implemented using a directional coupler or other coupling means.

〔Effect of the invention〕

As explained above, in a large number of slave devices, the number of parts is small and economical by using a transmitting/receiving element, and even if a single main device has a large number of parts and becomes expensive, the overall effect is small. small. Furthermore, if separate light-emitting elements and light-receiving elements are provided, communication efficiency can be improved as well.

Therefore, an economical and efficient method of communication is obtained.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram of an apparatus according to an embodiment of the present invention. Figure 2 is a wavelength characteristic diagram of the transmitting/receiving element. FIG. 3 and FIG. 4 are configuration diagrams of a conventional device. A...Main device, B r -B n...Slave device, C.
... Star coupler, F... Optical fiber, M... Coupling mirror, S... Light emitting element, R... Light receiving element, SR
...An element used for both transmission and reception.

Claims (3)

[Claims] (1) One main device and multiple slave devices are connected by a transmission line including an optical fiber and a branching/coupling circuit, and the transmission path is such that the optical signal transmitted by the main device reaches all the slave devices. , the optical signal transmitted by one of the slave devices is configured to reach at least the main device, and in an optical fiber bidirectional transmission system that includes means for switching transmission and reception in a time-division manner, the main device has an optical signal on the transmission path. A light emitting element for transmitting a signal and a light receiving element for receiving an optical signal from the transmission line are separately provided, and the slave device is equipped with a transmitter/receiver element for transmitting and receiving an optical signal to the transmission line. Optical fiber bidirectional transmission method. (2) The optical fiber bidirectional transmission system according to claim (1), wherein the branching and coupling circuit is a star coupler. (3) The emission wavelength of the light emitting element of the main device approximates the wavelength of maximum light receiving sensitivity of the light receiving element of the slave device, and the maximum light receiving sensitivity wavelength of the light receiving element of the main device approximates the light emission wavelength of the light emitting element of the slave device. The characteristics of each element are selected in claim No. (
The optical fiber bidirectional transmission method described in item 1).