JPS6030455B2 - optical transmission equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides an optical transmission device that connects a center and a plurality of terminals with a single line and performs bidirectional transmission by using a plurality of wavelengths.

Conventionally, as a method of connecting a center and a plurality of terminals in an optical fiber transmission device, as shown in Fig. 1a and b, each terminal 2 to 6 and the center 1 are connected with a separate line, or a direction is used. Possible methods include a method of connecting using couplers 8 to 14, and a method of connecting using a duplexer. The individual connection method shown in Figure 1a can provide a large optical output and does not require a splitter or demultiplexer, but it has the drawbacks of requiring an input light source for each line and requiring a large amount of transmission fiber. ing.

Furthermore, in the case of bidirectional transmission, additional fibers of the same distance are required, or devices such as branchers and duplexers are required. FIG. 1b shows the case where a directional coupler is used.

Reference numeral 7 indicates a center configuration, and 8 to 14 indicate terminal portions each consisting of a branch having a four-terminal configuration.

A part of the optical signal 15 output from the center 7 is branched to a fiber 17 at a terminal 8 and the rest is transmitted to a terminal 9. On the other hand, part of the optical signal input from the fiber 16 is transmitted to the terminal 9 and the rest to the fiber 17. Therefore, the loss of the transmitted optical signal is not only very large, but also
If the output signals of 7 are in the same wave number band, transmission and reception cannot be performed at the same time. Also, fiber 6
It also has the drawback of crosstalk in that the input optical signals from the terminals 9, 10, . . . , 14 can also be received by the terminals. SUMMARY OF THE INVENTION Therefore, the present invention provides an apparatus that eliminates crosstalk between terminals and allows bidirectional transmission between the center and each terminal. The present invention will be described below based on examples using the drawings.

FIG. 2 shows one row of the basic configuration of the duplexer of the present invention.

20, 21, 22, 23 are optical fibers 24, 25
, 26, 27 are Shinzu series.

Reference numeral 28 indicates a wavelength separation filter made of a dielectric multilayer film attached at an angle of 45° with respect to each fiber axis.

Now, assuming that the characteristics of the fiber 28 are as shown in Fig. 3, the optical signal in the r wavelength band is transmitted, and the light in the two wavelength bands is reflected. Suppose that light in the wavelength band 2 is incident. It is made into a parallel beam by the lens 24, and the optical signal in the wavelength band r is transmitted by the filter 28 and transmitted to the fiber 22. The light in the wavelength band 2 is reflected. At the same time, the optical signal in the r2 wavelength band is reflected from the fiber 21 and transmitted to the fiber 22.The optical signals transmitted to the fiber 21 and the fiber 23 are those in the same wavelength band. Although it is a carrier wave, the transmission signals do not need to be the same.Filter 28
An optical signal r3 whose characteristics are as shown in FIG.
, ``4'' is input from the fiber 20, the optical signal in the r3 wavelength band is propagated to the fiber 23, and the optical signal in the r4 wavelength band is propagated to the fiber 22.

Note that such a function can be obtained by a configuration in which a self-converging lens and a filter are combined in addition to the above configuration. As described above, according to the present invention, optical signals in multiple wavelength bands can be demultiplexed for each wavelength band, and at the same time, another signal can be superimposed on another transmission fiber using the same wavelength band carrier wave.

Now, consider a state in which elements having the configuration shown in FIG. 2 and the characteristics shown in FIG. 4 are connected in a chain as shown in FIG. 5.

^, , ^2...Input n represents the carrier wave band of the optical signal in order from the shortest wavelength, and as shown in FIG. 4, it coincides with the reflection wavelength band of each element. Therefore, the input optical signals entering element A, ~input n, are separated only from the optical signals in the wavelength band, and are separated into ~2~
The remaining signal at input n is obtained by multiplying another signal in the wavelength band by B
transmitted towards the element. Similarly, the B element performs demultiplexing of two input wavelength bands and coupling of optical signals of two other input wavelength bands.
In this way, the signals in the short wavelength band are sequentially separated and combined, and after passing through N elements, the newly combined input, to input n signals propagate. An example of applying such a system to a system is shown in Part 6.
Shown in Figure 0.

The center 29 and the terminals 30-36 are connected in a ring. Optical signal sent from center 29^. - input 8 allows each of the terminals 30 to 36 to independently receive only signals in the wavelength band corresponding to the respective terminal. Further, each terminal 30 to 36 can transmit only to the center 295. By adopting a closed circuit configuration in this manner, it is possible to configure a system in which transmission and reception are possible only between each terminal and the center, without mutual communication between the terminals. Note that in the systems shown in FIGS. 5 and 6, the system according to the present invention can be further connected to each element or each terminal. For example, connect A,, A2, . . . An to element A in Fig. 5, and input 1, ^, 2, . . . for each element.
A predetermined purpose can be achieved by separating and inputting ^ and n. In addition, in Fig. 5, all of the elements A to N are composed of bandpass filters, but the first stage A element reflects (transmits) the signal in the input wavelength band and transmits (reflects) the signal in the input wavelength band. The short wavelength side reflection (transmission) filter can be replaced by a filter that transmits (reflects) light with a longer wavelength than the input n wavelength band in the final stage N element. Similarly, in the filter shown in FIG. 3, a similar system can be constructed by simply changing the terminal positions.
Next, FIG. 7 shows a repeater configuration in a multi-wavelength multiplexed optical fiber transmission system.

37 and 38 are input and output fibers, and 42 to 49 are fibers.

Reference numerals 39, 40, and 41 indicate optical demultiplexing elements having mirror characteristics similar to those shown in FIG. 5, which are arranged in a line with their axes aligned.

Reference numerals 50, 51, and 52 indicate light emitting portions having emission wavelengths corresponding to the filter characteristics of 39, 40, and 41.

Similarly, reference numerals 53, 54, and 55 indicate light receiving sections corresponding to each filter characteristic.

Now, when an optical signal whose carrier wave is in each wavelength band from input to input n is propagated from the fiber 37, it is input at the filter section 39. The wavelength band signal is reflected and converted into an electrical signal by the light receiving element 53, and after relay processing such as shaping and amplification of the signal waveform is performed, the light emitting unit 50 is driven and input again, and the optical signal in the wavelength band is converted into an electric signal. It is combined with the optical signals input 2 to input n that have been reflected and transmitted by the mirror 39, and is propagated to the b element section. Similarly, in the b element section, the optical signal in the two wavelength bands is relayed and propagated to the main transmission path again. All the optical signals in the input to input n wavelength bands that have been relayed in this way are transmitted to the fiber 38. Therefore, by adopting such a method of filtering and inputting optical signals, it is possible to configure the receiver and transmitter with approximately half the number of elements compared to configuring the receiver and transmitter with separate demultiplexing and multiplexing elements. Can be done. As explained above, the present invention provides the following effects.

[1] A closed-loop optical transmission system can be constructed by having a center configuration having a transmitting and receiving section for optical signals in multiple wavelength bands and a plurality of terminal sections having transmitting and receiving sections for optical signals in a small number of wavelength bands.

(2) In the above closed-loop system, each terminal can have a transmission and reception end with little optical loss.

'3' In the closed loop system described above, the center section and the terminal section can perform bidirectional transmission, and the system configuration is such that there is no crosstalk between the terminals.

(4) In a repeater configuration for optical signal amplification, waveform shaping, etc., the number of elements is small, and a highly reliable and efficient repeater configuration can be achieved.

[Brief explanation of the drawing]

1a and 1b are block diagrams of a conventional multi-terminal connection device, FIG. 2 is a block diagram of a duplexer according to the present invention, FIGS. 3 and 4 are characteristic diagrams of filters, and FIG. FIG. 6 is a block diagram showing each embodiment of the present invention, and FIG. 7 is a block diagram of a multi-wavelength repeater showing another embodiment of the present invention. 20-23, 37, 38... Optical fiber, 24
~27,45,46...Lens, 28,39~41...
... Semi-transparent mirror, 29 ... Center, 30-36
, A to N... terminal device. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1. A filter having a characteristic of reflecting light in a specific wavelength band and transmitting light in other wavelength bands, and a plurality of lights within a band including both the reflection and transmission wavelength bands of the filter. a first optical transmission means for inputting a first signal consisting of a signal into the filter; and a second transmission means for receiving and transmitting a second signal of the first signal that has passed through the filter. , a third transmission means for receiving and transmitting a third signal reflected by the filter among the first signals, and a signal having a narrower wavelength band among the second and third signals; a fourth transmission means for transmitting a fourth signal having a wavelength band, and transmitting a fifth signal obtained by transmitting or reflecting the fourth signal through the second and third filters. An optical transmission device characterized in that the second and third signals and the fifth signal are superimposed by inputting the signal to one of the transmission means that receives a signal having a wide wavelength band. 2. The first transmission means is installed in the input section, and the one receiving the signal in a wider wavelength band among the second and third transmission means is installed in the output section. Claim 1, wherein each filter in each unit element has a different transmission or reflection wavelength band, and each unit element has its input part and output part connected to each other. optical transmission equipment.