JPH0429427A - Bidirectional optical transmission equipment - Google Patents

Abstract

PURPOSE:To transmit the different kinds of signals of a video signal and slow speed data, etc., over a long distance by decreasing the loss of an optical branching/coupling device at the signal side with low level difference between transmission and reception, and increasing the loss allocated to a transmission line. CONSTITUTION:An electrical video signal is converted to an optical signal by an electro-optic converter 11, and is transmitted passing the optical branching/coupling device 12 with transmission factor 80%, and transmits an optical branching/coupling device 14 with transmission factor 80%, and is recovered to an original video signal by an opto/electric converter 15. Meanwhile, electrical slow speed data is converted to the optical signal by an electro/optic converter 16, and is transmitted by reflecting on the optical branching/coupling device 14 with reflectance 20%, and is reflected on the optical branching/coupling device 12 with reflectance 20%, then, is recovered to original slow speed data by an opto/electric converter 17. In such a way, since the loss of the optical branching/coupling section at a video signal side with low level difference between transmission and reception is low, and that of the optical branching/coupling section at a slow speed data side with high level difference between transmission and reception is high, the video signal and the slow speed data can be transmitted over the long distance.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a device for bidirectionally transmitting different types of signals such as video signals and data using optical fibers.

Conventional technology FIG. 4 shows the configuration of a conventional bidirectional optical transmission device.

In FIG. 4, reference numeral 1 denotes an electric/optical converter (Elo) that converts an electric video signal into an optical signal. Reference numeral 2 denotes an optical branching coupler, which transmits the signal from the electrical/optical converter 1 at a predetermined transmittance and sends it to the optical fiber 3. The optical video signal transmitted through the optical fiber 3 is transmitted through the optical branching coupler 4 at a predetermined transmittance. 5 is light that converts optical video signals into electrical signals/
It is an electrical converter (0/E) and restores the optical signal transmitted through the optical branching coupler 4 to the original video signal.

Reference numeral 6 denotes an electrical/optical converter (Elo) that converts electrical low-speed data into an optical signal, and the optical signal converted by the electrical/optical converter 6 is input to the optical branch/coupler 4. The optical branching coupler 4 reflects the optical signal from the electrical/optical converter 6 at a predetermined reflectance, and sends the reflected optical signal to the optical fiber 3. The low-speed optical data transmitted through the optical fiber 3 is reflected at a predetermined reflectance by the optical branching coupler 2 and sent to the optical/electrical converter 7 (0/E') that converts the low-speed optical data into an electrical signal. is input. The low-speed data of the light reflected by the optical branching coupler 2 is restored to the original low-speed data by this optical/electrical converter 7.

As shown in FIG.
It was 0%. That is, an optical branching coupler with a transmission loss and a reflection loss of 3 dB was used.

Next, the operation of the conventional example will be explained in more detail with reference to FIG. FIG. 6 shows a level diagram in the conventional example, where pov is the video signal side light emitting power and POD is the low speed data side light emitting power P.
rv is the received light power on the video signal side, pro is the received light power on the low-speed data side, MINP is the allowable received light power on the video signal side,
MINPrD indicates the allowable light reception power on the low-speed data side. Note that the allowable received light power refers to the received light power required for a required S/N or error rate.

Here, the optical fiber transmission line loss is α (dB/km),
Assuming that the transmission distance is T (%) and the transmittance of the L1 optical branching coupler, the received light power P on the video signal side and the received light power pro on the low-speed data side are expressed as follows.

prv=Pov-lQ 1ogT-a*L-1Q
1logT...(1) Pro=Pop-IQ log(1-T)-a ・
L-10log(1-T) ・=(2)
The maximum transmission distance L wax is determined from the following conditions.

Prv≧MINP, ■ ・−・(3)p
ro≧MINPrD (4) Normally, the allowable light reception level of a video signal is higher than that of low-speed data, and in this case, Lax is determined by the above equation (3). -For example po・=OdBm, POo=od
Bm, T=50%, α=ldB/km, MINPrv
= -10 dBm, MINPrt+= 22 dBm, L wax is 0-3-IXL-3≧-10 from the above equations (1) and (3), and l*ax=4 (km).

In this way, the conventional bidirectional optical transmission device described above can also bidirectionally transmit video signals and low-speed data by using an optical branching coupler with a transmittance of 50% and a reflectance of 50%.

Problems to be Solved by the Invention However, in the conventional bidirectional optical transmission device, the transmission line loss on the video signal side where the level difference between the transmitter and the receiver is small ((emission power) - (allowable received light power)) and the level difference between the transmitter and the receiver are reduced. The problem is that since the transmission path loss on the large low-speed data side is the same, the transmission distance is determined by the transmission path loss on the video signal side with a small level difference between sending and receiving, making it impossible to transmit video signals and low-speed data over long distances. was there.

The present invention solves these conventional problems and aims to provide an excellent bidirectional transmission device capable of long-distance transmission.

Means for Solving the Problems In order to achieve the above object, the present invention reduces the transmission loss or reflection loss of the optical branching coupler on the signal side where the level difference between transmitting and receiving is small, and reduces the transmission loss or reflection loss on the signal side where the level difference between transmitting and receiving is large. The transmission loss or reflection loss of the optical branching coupler is increased.

Therefore, according to the present invention, it is possible to increase the loss allocated to the transmission line section on the signal side where the level difference between the transmitter and the receiver is small, and it is possible to transmit different types of signals such as video signals and low-speed data over long distances. It has the effect of being able to.

Embodiment FIG. 1 shows an embodiment of the present invention, which has the same configuration as the conventional example shown in FIG. 4, but differs in the configuration of the optical branching coupler. In FIG. 1, reference numeral 11 denotes an electrical/optical converter (EO) that converts an electrical video signal into an optical signal;
Reference numeral 2 denotes an optical branching coupler that transmits the optical signal converted by the electrical/optical converter 11 with a predetermined transmittance and reflects the optical signal sent from the optical fiber 13 with a predetermined reflectance.
3 is an optical fiber that transmits the optical signal output from the optical branching coupler 12; 14 is an optical fiber that transmits the optical signal transmitted through the optical fiber 13 at a predetermined transmittance;
An optical branching coupler that reflects the optical signal from the optical converter 16 with a predetermined reflectance, 15 an optical/electrical converter (OE) that converts the optical signal from the optical branching coupler 14 into the original video signal, 16 is an electrical/optical converter (
EO), 17 is an optical/electrical converter (OE) that restores low-speed optical data transmitted through the optical fiber 13 to low-speed electrical data.

The optical branching couplers 12 and 14, as shown in FIG.
The one used has a transmittance of 80% and a reflectance of 20%.

Next, the operation of the above embodiment will be explained. The electrical video signal is converted into an optical signal by an electrical/optical converter 11, passed through an optical branching coupler 12 with a transmittance of 80%, and transmitted through an optical fiber 13. The optical signal incident on the optical branching coupler 14 on the other side passes through the optical branching coupler 14 with a transmittance of 80%, and is restored to the original video signal by the optical/electrical converter 15. On the other hand, low-speed electrical data is converted into an optical signal by an electrical/optical converter 15, reflected by an optical branching coupler 14 with a reflectance of 20%, and transmitted through an optical fiber 13. The optical signal incident on the optical branch/coupler 12 on the other side is reflected by the optical branch/coupler 12 with a reflectance of 20%, and is converted into the original low-speed data by the optical/electrical converter 17.

FIG. 3 shows a level diagram of the embodiment described above. The loss of the optical branching/coupling section on the video signal side of the optical branching/coupling section 12.14 is approximately 1 dB (-1QIQII0.8), and the loss of the optical branching/coupling section on the low-speed data side is approximately 7 dB (-101og0
．． 2). Therefore the electrical/optical converter 11.16,
When the characteristics of the optical/electrical converter 15, 17 and the optical fiber 13 are the same as those of the conventional example, that is, Pov=Q d
B m, POD=OdBm, a=1dB/km,
MINPrv=-10dBm, MINPrD=-22d
In the case of Bm, the maximum transmission distance RL-x is as described in (1) and (3) above.
From the formula, 0-1-IXL-1≧-10, and Lmax=8 (km).

Also, from equations (2) and (4) above, 0-7-IXL-7≧-22, 1-may=8 (km).

As a result, it becomes possible to transmit twice as much as the L port x=4 and 1H in the conventional example.

Thus, according to the embodiment, the optical branching coupler 12.
Optical fiber 13
It has the advantage that a large loss can be allocated to the transmission line section, and video signals and low-speed data can be transmitted over long distances.

Effects of the Invention As is clear from the embodiments described above, the present invention reduces the loss of the optical branching coupler on the signal side with a small level difference between transmitting and receiving,
By increasing the loss allocated to the transmission path,
This has the effect that the transmission distance can be extended, and different types of signals such as video signals and low-speed data can be transmitted over long distances.

[Brief explanation of the drawing]

FIG. 1 is a schematic block diagram of a bidirectional optical transmission device showing an embodiment of the present invention. FIG. 2 is a diagram showing the ratio of transmittance and reflectance of an optical branching coupler in an embodiment of the present invention. 3 is a level diagram in an embodiment of the present invention; FIG. 4 is a schematic block diagram showing an example of a conventional bidirectional optical transmission device;
FIG. 5 is a diagram showing the ratio of transmittance and reflectance of an optical branching coupler in a conventional example, and FIG. jK6 is a diagram showing a level diagram in the conventional example. 11... Electric/optical converter for video signal, 12.14...
- Optical branching coupler, 13... Optical fiber, 15... Optical/electrical converter for video signals, 16... Electrical/optical converter for low-speed data, 17... Optical/electrical converter for low-speed data. vessel.

Claims (1)

[Claims] The insertion loss of the optical branching/coupling device is reduced for the first signal with a small difference between the transmitted optical power and the allowable received optical power, and the insertion loss of the optical branching/coupling device is reduced for the second signal where the difference between the transmitted optical power and the allowable received optical power is large. A bidirectional optical transmission device that increases transmission distance by increasing insertion loss and increasing loss allocated to a transmission path when optically transmitting a first signal and a second signal in both directions.