JPS59127003A - Optical attenuator - Google Patents

Abstract

PURPOSE:To set an optimum photodetection level for an optical wavelength multiplex transmission system which uses plural wavelengths and to constitute the optical transmission system of high quality by using an interference film filter which has the amounts of attenuation corresponding to the plural wavelengths. CONSTITUTION:Light of wavelength lambda1 from the electrooptic transducing circuit 31 of an optical terminal station device 3 is converted into a parallel beam through a rod lens RL1, and a part of wavelength lambda1 is attenuated by alpha through an optical attenuating element F1 having a characteristic curve (a) as shown in a figure (c), converged by a rod lens RL2, and then sent to the photoelectric transducing circuit 42 of an optical terminal station device 4. On the other hand, light of wavelength lambda2 from the electrooptical transducing circuit 41 of the optical terminal station 4 is converted into a parallel beam through the rod lens RL2, and a part of wavelength lambda2 is attenuated by beta through an optical attenuating element F2 with a characteristic curve (b) ina figure (c) and sent to the optical terminal station device 3. Therefore, the light-wavelength lambda to light-loss characteristic of an optical attenuator 106 shown in a figure (a) is as shown in a figure (b) and the components of light wavelengths lambda1 and lambda2 are attenuated optically by the different amounts.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an optical attenuator that is used for optical wavelength multiplexing and transmission and can set an arbitrary optical attenuation amount for light of a specific wavelength.

(Prior art) When transmitting light of multiple wavelengths through a single optical fiber, such as in optical wavelength division multiplexing transmission, an optical attenuator is required when the distance is short and the received light level is too high. Generally, the optical attenuator had an optical attenuation that did not change depending on the optical wavelength.

FIG. 1 shows an example of a bidirectional optical transmission system that does not use an optical wavelength division multiplexing transmission system, in which 1 and 2 are optical terminal equipment;

21 is an electro-optical conversion circuit, 12.22 is an opto-electric conversion circuit,
101 and 102 are optical fibers, and 103 and 104 are optical attenuators that do not have conventional optical wavelength characteristics. As shown in FIG. 1, each optical transmission system has one optical fiber 101,
102, it becomes possible to insert optical attenuators 103 and 104 with optimal attenuation amounts into the respective transmission systems.

FIG. 2 shows the optical wavelength (λ) vs. optical loss (1oss) characteristics of the optical attenuators 103 and 104.
3,104 optical wavelengths λ1. It is shown that they have optical loss characteristics of α and β, respectively, corresponding to λ2.

When performing bidirectional transmission with a single optical fiber using an optical attenuator that does not have conventional optical wavelength characteristics, there is a drawback that it is not always possible to set the optimal light reception level for all optical wavelengths. Since it has optical wavelength characteristics, the transmission level is not constant depending on the optical wavelength, and therefore the light receiving sensitivity of the light receiving section is not constant. Also, if you try to adjust the light receiving level using a conventional optical attenuator that does not have optical wavelength characteristics, even if the light receiving level is optimal in one system, the light receiving level in the other system will be too high and the light receiving part will become saturated. (Objective of the Invention) In order to eliminate these drawbacks, the object of the present invention is to make it possible to arbitrarily set the amount of optical attenuation depending on the optical wavelength. This will be explained in detail below.

(Structure of the Invention) The present invention is characterized in that it is composed of a plurality of optical attenuation elements whose optical attenuation varies depending on the optical wavelength, and the optical attenuation varies according to multiple types of optical wavelengths that are multiplexed. This is an optical attenuator.

(First Embodiment) FIG. 3 shows an example of a bidirectional optical transmission system using one optical fiber, in which 3 and 4 are optical terminal devices, and 31 and 41L are electrical conversion circuits 1. ? 2.42 is a photoelectric conversion circuit, 1
05.107 is an optical multiplexer/demultiplexer, 106 is an optical attenuator according to an embodiment of the present invention, and 10B is an optical fiber.

FIGS. 4(a), 4(b), and 4(c) illustrate the optical attenuator 106. FIG. FIG. 4(a) shows a structural diagram of the optical attenuator 106, in which RLI and RL2 are an opening, a drain lens, and an F for converting light from an optical fiber into a parallel beam or concentrating a parallel beam to enter the optical fiber, respectively. 1. F2 is an optical attenuation element (interference film filter), FIG. 4(b) is a characteristic diagram of optical wavelength (λ) versus optical loss (1oss) of the optical attenuator 106,
FIG. 4(c) shows the optical attenuation element F1. A characteristic diagram of optical wavelength (λ) versus optical loss (1oss) corresponding to F2 is shown.

In FIGS. 3 and 4, light with a wavelength λ1 from the electro-optical conversion circuit 3 of the optical terminal device 3 passes through the rod lens RI, 7 and is converted into a parallel beam, with the characteristics shown in FIG. 4(c). curve a
The wavelength portion of λ1 is α
After receiving the attenuation amount, the light is focused by the rod lens RL2 and sent to the opto-electric conversion circuit 42 of the backlight terminal device 4. Further, the light of wavelength λ2 from the electro-optical conversion circuit 41 of the optical terminal equipment 4 is converted into a parallel beam through the rod lens RL2, and the light of wavelength λ2 is converted into a parallel beam by the optical attenuation element F2 having the characteristic curve shown in FIG. 4(c). The wavelength portion receives an attenuation amount of β and is sent to the optical terminal device 3. Therefore, the optical wavelength (λ) vs. optical loss characteristic (1oss) of the optical attenuator 106 shown in FIG. 4(a) is as shown in FIG. 4(b).
), and the optical wavelength λ1. A different amount of optical attenuation is given to each of λ2.

In this way, by preparing optical attenuation elements (interference film filters) that provide different amounts of attenuation for each system, it becomes possible to set the optimal light reception level for each system, which This has the advantage of being able to eliminate the above-mentioned drawbacks.

(Second Embodiment) FIG. 5 shows another example of a bidirectional optical transmission system using one fiber, and 109 and 110 are optical fibers provided for each of the optical terminal equipment 3 and the optical terminal equipment 4. is an attenuator,
The light receiving level can be optimally adjusted at the 3° and 4 position of each optical terminal device.

6(a) and 6(b) explain the optical attenuator 109, FIG. 6(a) is a structural diagram of the optical attenuator 109, and FIG.
Figure (b) shows the optical attenuation amount (λ) versus the optical wavelength (λ) of the optical attenuator 109.
1oss) characteristics. Similarly, FIG. 7(a) is a structural diagram of the optical attenuator 110, and FIG. 7(b) shows the optical wavelength (λ) vs. optical attenuation (1oss) characteristic of the optical attenuator 110.

This embodiment will be explained using FIG. 5, FIG. 6, and FIG. 7.

The light of wavelength λ from the electro-optical conversion circuit 31 of the optical terminal station-3 is not attenuated at all by the optical attenuator 109, and is not attenuated by the optical attenuator 110.
Then, the attenuation amount α shown in FIG. 7(b) is received and sent to the optical terminal device 4. Further, the laser beam of wavelength λ2 from the electro-optic converter circuit 4 of the optical terminal equipment 4 is not attenuated at all by the optical attenuator 110, and is attenuated by the optical attenuator 109 as shown in FIG. 6(b). β is received and sent to the optical terminal device 3.

In this way, an optical attenuator is provided on each optical terminal equipment side,
Even if the received light levels are adjusted individually, there is an advantage that the drawbacks of the conventional method can be eliminated, as in the case of the first embodiment.

(Third Embodiment) Next, an optical attenuator used in the multiwave bidirectional optical wavelength division multiplexing transmission system and provided on each side of the optical terminal equipment will be described.

Figure 8 shows an example of a multiwave bidirectional optical wavelength division multiplexing transmission system.
6 is an optical terminal device consisting of n electro-optical conversion circuits 511 to 51n, n photo-electric conversion circuits 521 to 52n, and an optical multiplexer/demultiplexer 113, and transmits and receives light of n different wavelengths;
111.112 is an optical attenuation device according to the embodiment of the present invention, which is composed of 621 to 62n of electro-optic conversion circuits and 611 to 61n of photo-electric conversion circuits, and performs transmission and reception of 9 wavelengths of n types. 1o8 is an optical fiber.

The optical attenuator 11 inserted into the optical terminal equipment 5 side will be explained with reference to FIG. FIG. 9(a) shows a structural diagram of the optical attenuator 111, and RL7. RL2 is a port that converts laser light into a parallel beam or focuses a parallel beam.

Drain lens, F21 to F2n are n types of light wavelengths λ21 to λ
An optical attenuation element (interference film filter) that has optical attenuation characteristics corresponding to 2n and can be manufactured using a known interference film filter manufacturing technique, FIG. 9(b) shows the optical wavelength (λ) of the optical attenuator 111.
FIG. 9(c) shows a characteristic diagram of optical loss (1oss) versus optical wavelength (λ) corresponding to optical attenuation elements F2x to F2n (for example, optical attenuation element F21
In this case, the maximum optical attenuation is performed at the wavelength λ21, and no optical attenuation is performed at other optical wavelengths). Similarly, the first
0(a) is a structural diagram of the optical attenuator 112 in FIG.
Figure (b) shows the optical wavelength (λ) of the optical attenuator 112 versus the optical loss (1
oss ) characteristic diagram, Figure 10(c) shows the optical attenuation element Fil.
~ Optical wavelength (λ) corresponding to Fin vs. optical loss (1oss
) shows the characteristic diagram.

In this case as well, as in the case of transmitting light of two types of wavelengths in the second embodiment, the wavelengths of λ1 to λ1n sent from the electro-optical conversion circuits 511 to 51n of the optical terminal equipment 5 are The light of n different wavelengths is not attenuated at all by the optical attenuator 111, but is subjected to attenuation amounts β1 to βn corresponding to the respective wavelengths λ11 to λ1n by the optical attenuator 112, as shown in FIG. 10(b). The signal is sent to the optical terminal device 6. Similarly, the electro-optical conversion circuit 621~
The light of n types of wavelengths λ21 to λ2n transmitted from the optical attenuator 112 is not attenuated at all by the optical attenuator 112.
As shown in FIG. 9(b), each wavelength λ21 to λ
In response to the attenuation amounts α1 to αn corresponding to 2n, the optical terminal equipment 5
sent to.

As described above, if the optical attenuator according to the embodiment of the present invention is used in a multiwave bidirectional optical wavelength division multiplexing transmission system, an optimal light reception level can be set for each optical transmission system. In the case of this embodiment, there are two types of wavelengths in the second embodiment.
The present invention is expanded to different types of wavelengths and attenuated correspondingly to each wavelength, and the conventional drawbacks can be solved in the same way as the other embodiments described above.

(Fourth embodiment) FIG. 11 shows the optical attenuator 111 and optical attenuator 1 shown in FIG.
An example of a multiwave bidirectional optical wavelength division multiplexing transmission system using one optical attenuator 115 having 12 functions is shown (symbols are the same as in FIG. 8).

FIGS. 12(a), 12(b), and 12(c) illustrate the optical attenuator 115. FIG. FIG. 12(a) shows a structural diagram of the optical attenuator 115, the symbols are the same as those in FIG. 9(a) and FIG. 10(a), and FIG. 12(b) shows the structure of the optical attenuator 115. Optical wavelength (λ) vs. optical loss (1oss) characteristic diagram, Figure 12 (
c) are optical attenuation elements F 11 to F I n , F 21
~ Optical wavelength (λ) corresponding to F 2 n vs. optical loss (1 os
In Figures 11 and 12, light of wavelengths (λII to λ7n) sent from the electro-optical conversion circuits 511 to 51n of the optical terminal device 5 passes through the drain lens RL7 and becomes a parallel beam. The light is converted into a light beam, subjected to corresponding attenuation by the light attenuation elements Fll to Fin having the characteristic curve shown in FIG. ,
The signals are sent to the photoelectric conversion circuits 611 to 61n of the optical terminal device 6, respectively. Moreover, the electro-optical conversion circuit 6 of the optical terminal device 6
Wavelength sent from 21 to 62n7J・(λ21 to λ2n)
The light is from the mouth, drain RL, ? The optical attenuator F2 is converted into a parallel beam through the optical attenuator F2 and has the characteristic curve shown in FIG.
1 to F2n (not attenuated by the optical attenuation elements Fll to Fin), the rod 1
After the light is collected by the /ns RLI, it is sent to the opto-electrical conversion circuits 521 to 52n of the optical terminal device 5, respectively.

In this way, by preparing optical attenuation elements (interference film filters) that provide attenuation amounts corresponding to multiple different wavelengths, it is possible to set the optimal light reception level for each system. , has the advantage of eliminating the conventional drawbacks as in the case of the other embodiments of the present invention.

(Effects of the Invention) The optical attenuator of the present invention can have an arbitrary amount of optical attenuation for a specific wavelength, so it can provide the optimal light reception level for an optical wavelength division multiplexing transmission system that uses multiple wavelengths. It is possible to configure a high-quality optical transmission system.

[Brief explanation of the drawing]

Figure 1 is an explanatory diagram of a bidirectional optical transmission system that does not use an optical wavelength division multiplexing transmission system, and Figure 2 is a conventional optical attenuator 10 shown in Figure 1M.
,? , 104 optical wavelength (λ) vs. optical loss (1oss
3 is an explanatory diagram of a bidirectional optical transmission system using one optical fiber, FIG. 4 is an explanatory diagram of an optical attenuator 106 according to an embodiment of method 1 of the present invention, and FIG. FIG. 6 is an explanatory diagram of an optical attenuator 109 according to an embodiment of method 2 of the present invention, and FIG. 7 is an explanatory diagram of another bidirectional optical transmission system using optical fibers. An explanatory diagram of the optical attenuator 110, FIG.
FIG. 9 is an explanatory diagram of a multiwave bidirectional optical wavelength division multiplexing transmission system using optical fibers, and FIG. 9 is an optical attenuator 11 according to an embodiment of method 3 of the present invention.
1, FIG. 10 is an explanatory diagram of the optical attenuator 112 according to the embodiment of method 3 of the present invention, and FIG. 11 is an explanatory diagram of another multi-wave bidirectional optical wavelength division multiplexing transmission system using one optical fiber. Figure, 12th
The figure is an explanatory diagram of an optical attenuator 115 according to an embodiment of method 4 of the present invention. 3+ 4 H5+ 15 Optical terminal equipment 1. ? 1,
41. 5 No. 1-51n, 621-62n ・Electro-optical conversion circuit, 32, 42, 521-52n, 611-6
7n photoelectric conversion circuit, 106, 109, 110° 111
．． 112.115 ・Optical attenuator, 105°107.1
13,114-Optical multiplexer/demultiplexer, 708-Optical fiber, RL
I, RLI rod lens, F 1, F 2,
F 11 - F I n , F 21 - F 2 n
- Optical attenuation element. Il+ (b) AI+ Al1 Al1 Person Ir1All
AZ2AZ3 A<n 1ff-1 (8) Figure 9 (C) 8ll Ha12 'L13 Ha1 Nov
1 u2 8t3 8211 yztλ
) Procedural amendment (Mutsu) 5B, 4.22 Showa year, month, day, Japan Patent Office Commissioner, 1, Indication of the case, 1988 Patent Application No. OO2296 Volume 2, Name of the invention Optical attenuator 3 Person making the amendment Related patent application office (
105) 1-7-12-4 Toranomon, Minato-ku, Tokyo.
Agent address (105) 1-7-1 Toranomon, Minato-ku, Tokyo
Item 2 will also be amended as per the attached sheet.
゛ ′) a4. Z2(1) Delete the statement ``The output level is not constant, therefore,'' in lines 18 to 19 of page 2 of the specification. (2) In the 3rd line of page 8 of the same book, the word ``largest'' is replaced by ``-''
The minimum is corrected. (3) Drawings "Figure 5" and [Figure 12 (a) (no change in content) (b) (C) J will be corrected as shown in the attached sheet. Figure 5

Claims (1)

[Claims] 1. An optical attenuator comprising a plurality of optical attenuation elements whose optical attenuation varies depending on the optical wavelength, and whose optical attenuation varies according to a plurality of types of optical wavelengths that are multiplexed and transmitted.