JPS6248820A - Two-way optical wavelength converter - Google Patents

Abstract

PURPOSE:To exchange mutually a signal transmission wavelength in both fibers without requiring two each quartz systems and plastic fibers by providing an optical wavelength conversion path composing of a polarized beam splitter and a Farady element. CONSTITUTION:Infrared rays irradiated from a quartz system optical fiber 1 are subject to linearly polarization through a polarizer 51, a half wavelength plate 61 and a Farady element 71. Then the rays are converted into visible rays through a light source 10, a polarized beam splitter 91 and a frequency component 11. The visible rays are made incident on the optical fiber 2 via an optical wavelength converting path composing of a polarized beam splitter 92 transmitting the visible rays only, a Farady element 72, a half wavelength plate 72 and a polarizer 52. The visible rays progress reversely from the fiber 2, are reflected in the splitter 92 and made incident on the fiber 1 via opposite paths through reflecting mirrors 93, 94. Thus, no two each of quartz systems and plastic fibers are required and the signal transmission wavelength in both the fibers is exchanged mutually.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an optical communication system that connects a quartz-based i7 fiber and a plastic fiber (-1) In particular, bidirectional optical wavelength conversion capable of bidirectional information transmission. This is related to the installation fllK.

In recent years, the use of plastic optical fibers as well as silica-based optical fibers has been promoted in optical communications.

This is because although plastic fibers have higher transmission loss than silica-based optical fibers, by increasing the core diameter to 1 silk, they are much easier to handle, such as easier end-face treatment and splicing. It is increasingly being used in cases where the signal transmission distance is short and transmission loss is not a big problem, for example, in subscriber system transmission lines, and in this case costs are also reduced.

That is, when considering information transmission within a company, quartz-based optical fibers are used for long-distance information transmission between offices, and plastic fibers are used for short-distance information transmission between offices.

In general, the signal transmission wavelength in a silica-based optical fiber is approximately 163μ, taking into account various conditions such as the loss characteristics of the transmission line and the transmission capacity.
m or about 1.5 μm in many cases, but in the case of plastic fibers, it is often set to visible light having a wavelength of 0.6 μm, which is the low loss region of plastic fibers. Therefore, in the above-mentioned example of information transmission within a company, for example, infrared x't propagated from one business office to another through a quartz FI7 fiber, is converted into an electrical signal by a photoreceiver, and then amplified. A commonly used method is to convert the aforementioned infrared light into visible light by driving a light emitting device such as a semiconductor laser or light emitting diode that emits visible light after signal processing such as waveform shaping. .

Conventionally, an example of this type of information transmission on both sides is as shown in Figure 3.When transmitting information from a trunk system quartz optical fiber to a subscriber system plastic source fiber, first, a quartz optical fiber is used. The infrared light emitted from the infrared light is received by a light receiver 171 such as an Avalanche photo diode and converted into an electrical signal.The signal processing unit 181 performs signal processing such as amplification and waveform shaping, and then emits visible light. Semiconductor laser 1
91 to input visible light into the plastic original fiber 2, and conversely, when transmitting all information from the plastic original fiber to the quartz fiber, the visible light emitted from the plastic LT7 fiber 2' is input to the photodiode. After receiving the light and converting it into an electrical signal with a photodetector 172 such as 172, and performing signal processing Fl! such as amplification and handshape shaping in a signal 1A processing unit 182,
A semiconductor laser 192 that emits infrared light is driven to input the infrared light into the silica optical fiber 1'.

However, in this conventional example of transmitting the same information on both sides, two quartz fibers and two plastic optical fibers were used as a set for bidirectional communication, so the number of fibers was large, and the Fiff This has the disadvantage that the diameter of the cable becomes large, making it impossible to take advantage of the lightness of the fiber and reducing the efficiency of fiber use.

[Problems to be Solved by the Invention] The purpose of the present invention is to develop a bidirectional quaternary wavelength conversion device that solves the above-mentioned drawbacks, namely, the need for two quartz-based optical fibers and two plastic FT7Y fibers. It is about providing.

Means for Solving the Problems In order to solve all of the above-mentioned problems, the present invention provides a first polarizer that converts the output light of a silica fiber into a first linearly polarized light, and a first medium wavelength plate. , a first polarization plane rotation element, and a l-th
a first polarizing beam splitter that transmits the linearly polarized light of w,1 and reflects and combines the locally oscillated light; a frequency conversion component, a first daylight transmission filter, a second polarization beam splitter that transmits linearly polarized light having a specific polarization plane of visible light of a specific wavelength and reflects it to a credit union, and a second polarization plane rotation element. , a first source wavelength variable path that is incident on the plastic source fiber and includes a second medium wavelength plate and a second polarizer;
The light emitted from the plastic optical fiber passes through the 10th Yuanchohenhou path, and then passes through the second polarizer, the second Mlong plate,
The second polarization plane rotating element is moved by the vertical direction of the VC, becomes a second @-polarized state, and is reflected by the second polarization beam splitter.
A frequency conversion component of Mouse 2 consisting of a resonator including a nonlinear medium, a low-pass transmission filter and a second high-pass transmission filter that pass infrared light of a specific wavelength obtained as an output, and an era name changing means. returns to the first optical wavelength conversion path through a bypass consisting of a first polarization plane rotation element, a half-wave plate of Fragment 1,
It adopts a configuration similar to that of the second original wavelength changing path which proceeds in the order of the polarizer of the first polarizer and enters the silica-based optical fiber. Therefore, the infrared light A (for example, 1,300 μfti) emitted from the silica-based optical fiber is
) is the first original wavelength conversion #! + All in all, the first polarizer generates the lth linearly polarized light, producing a l.

The polarization plane is changed by 90 degrees by the long plate, and then rotated counterclockwise by 456 polarization planes by the polarization plane rotation element of Mouse 1, and the incident plane is changed to the polarization beam splitter of 1 for infrared light A. Since it enters as the M-ray damage light with the polarization direction perpendicular to the image, it is completely transmitted. Furthermore, this first polarized beam drift is 0iiiI, which is the same as that of the first linearly polarized light.
ft plane, and infrared light C (for example, 1.383 μm) from a local light source having a different wavelength is totally reflected and enters the first frequency conversion component together with the first linearly polarized light. This first
In the frequency conversion component of , the first @ line scratch light of visible light B (for example, 0.670 μm), which is the sum of the frequency costs of both infrared fi A and C, and the infrared light D, which is the difference (for example, 21% 7 μm). Linearly polarized light with the same polarization plane is obtained, and the first high-pass filter blocks infrared ft, A and C, and visible light B
Only the linearly polarized visible light B is transmitted, and roughly enters the second polarizing beam splitter for visible light B as linearly polarized light with seven polarization directions perpendicular to the plane of incidence, and only this linearly polarized visible light B is completely transmitted. . Next, this visible light B has its polarization plane rotated by 45 degrees counterclockwise by a second polarization plane rotation element, and the polarization plane is further changed by 90 degrees by a second half-wave plate.
It passes through a pJ2 polarizer and enters a plastic fiber.

- The visible light B (e.g. 0.67 μm) emitted from the plastic $7. The plane of polarization is changed by 90 degrees by the second half-wave plate, and the plane of polarization is changed by 4 degrees counterclockwise by the rotation element of the polarization plane.
59 polarization is rotated and enters the second polarizing beam splitter for visible light B as a ray-scarred light with a polarization direction parallel to the incident plane. It is reflected by a second polarizing beam splitter and enters a resonator containing a bypass second frequency conversion component. It is important to appropriately select the material and phase matching conditions for composing the communicator.
Visible light B is converted into infrared light A (for example, 1,300 μm) and infrared light C (f+1 is 1,383 μm). Furthermore, only the infrared light A is allowed to pass through the low pass filter and the second high pass filter, excluding visible light B and infrared light C. Next, this infrared light A enters the 10-polarized beam splitter by a 9-direction changing means such as a reflection plate as @ray light having a polarization direction parallel to the plane of incidence. The infrared $A is reflected by this first polarization beam splitter and returns to its original path, and is converted to 45 by the first polarization plane rotation element.
The plane of polarization is rotated counterclockwise, the plane of polarization is further changed by 90 degrees by the first half-wave plate, and the light passes through the first polarizer and enters the source fiber of the stone-based fiber.

Example Next, embodiments of the invention will be explained with reference to the drawings.

Part 1 of the present invention: FIG. 1(a) shows a complete block diagram of an AM example.
Referring to FIG. Signal transmission wavelength of fiber 2: 0.67 μm
and a first polarizer 51 that converts the 1.3 μm infrared element t emitted from the silica optical fiber 1 into a first directly polarized light, and a l-th half-wave plate. 61, a flat Faraday element 71 as a polarization plane rotator, a local excavation source light source 10 having the same polarization plane as the first direct M polarized light but a different wavelength, and the first Rintake polarized light. A first polarizing beam splitter 91 that transmits, reflects and multiplexes local oscillation lights of different wavelengths, and a first frequency conversion component made of a nonlinear medium that generates visible -f with a wavelength of 0.67 μm from this multiplexed light. 11, and the first one that passes visible light with a wavelength of 0.67 μm.
high-pass filter 11' and a wavelength of 0.67 μm.
a second polarizing beam splitter 92 that transmits only visible light whose polarization direction is perpendicular to the plane of incidence of @ line polarized light, a second 7-arrate element 72 as a polarization plane rotation element, and a second half-wave plate. 62 and a second polarizer 52, with a polarizer of 0.6
The first optical wavelength conversion path that enters the plastic fiber 2 and the wavelength 0.67 μm of visible light that is emitted from the plastic original fiber 2.
The visible light of m travels in the opposite direction, passes through the second beam splitter 92, and then passes through the second frequency conversion component formed by the common camera 121 including the nonlinear medium 12, and the low-pass filter. 13, a second high-pass filter 14, and nine reflecting mirrors 93 and 94 as direction changing means, and then reflected by the first polarizing beam splitter 91 and returned to the first optical wavelength conversion path. and a second optical wavelength conversion path which travels in the opposite direction and enters the quartz fiber optical fiber l.

Next, the operation of this embodiment will be explained using FIG.

In FIG. 1, the coordinate axes are determined as shown in FIG. 1(k) for convenience of later explanation.

That is, the positive direction of ztlq is taken as the original traveling direction emitted from the silica-based optical fiber l mentioned above, and the positive direction of the
The positive direction of the axes is taken to be perpendicular to the X and z axes, and the x, y, and z axes form a right-handed system in this order.

First, infrared light 401 with a wavelength of 1.3 μm emitted from the silica-based optical fiber 1 is polarized by a 111g1 polarizer 51 at an angle of 45° with respect to the positive direction of the X axis, as shown in fJfI1 diagram (b). t-converted into linearly polarized light 402. Next, the linearly polarized light 402 is transferred to a first half-wave plate 61 for a wavelength of 1.3 μm.
It is converted into linearly polarized light 403 that makes an angle of 45° with the negative direction of the X-axis, as shown in Figure 1 (C). The linearly polarized light 403 then enters the first 7-arade element 71, which is a polarization plane rotation element;
is obtained so that the polarization plane of the incident @ line side light is rotated by 45 degrees counterclockwise when viewed from the positive direction of the z-axis, so the output light 404 of the 77 Radhe element 71 of 2AI is The plane of polarization is in the xQb direction, that is, the direction perpendicular to the plane of the paper, as shown in FIG. 1(d) and 81. Next, the linearly polarized light 404 is
The first polarized beam enters the tin slitter 91 . The first polarizing beam splitter 91 transmits linearly polarized light having a wavelength of 1.3 μm and a polarization direction perpendicular to its plane of incidence. Furthermore, the first polarization beam splitter 91 has the above-mentioned @i polarization: yt, 4 emitted from the local light source 1G.
A wavelength of 1.383 μm that overlaps the plane of polarization in the 04 and 1 directions.
Linearly polarized infrared light 405 is also incident, and this polarization beam splitter 91 reflects it to produce ffl with a wavelength of 1.3 μm.
1n (t4 element 404 linearly polarized light with wavelength 1.383 μm 4
05 is combined to form 406, which enters the nonlinear medium 11 made of -CLiNbQa, and the linearly polarized light whose polarization plane is perpendicular to the plane of the paper has a visible light wavelength of 0.67μITI and a wavelength of 21.7μITI.
Infrared light of μm (total of 4tJ7) is generated,
Kaesong transmission filter (short e, long transmission filter) enters the IP with a wavelength of 0.67 μIn (7) 'afQ original 407' is 071 years old. Note that visible light 407' is linearly polarized light,
Its plane of polarization is perpendicular to the plane of the paper. Next, the aforementioned visible light 4
07' is incident on the polarization beam splitter 92 @2. 81!2 polarizing beam splitter 92 has a wavelength of 0.6
i'l with a polarization of 7 μm and perpendicular to its plane of incidence
The I line fi1 element is transmitted. The second polarizing beam splitter 92f, the transmitted beam 408 has the direction of the polarization plane
), as shown in FIG.
is incident on the Faraday element 72.

The second Faraday element 72 rotates the polarization plane of the incident linearly polarized light by 45° (b) counterclockwise when viewed from the positive direction of the z-axis.
Since the plane of polarization of the 111 emitted light 409 of the 7 Alade element 72 is as shown in Fig. 1 (
As shown in f), align 45° with the positive direction of the
It becomes A-polarized light. Next, the aforementioned emission-! 409 is wavelength 0
．． It enters the second half-wave plate 62 for 67 μm, and the 111th
The negative direction of the X-axis as shown in (g) and the angle of 45 degrees
It is converted into linearly polarized light 410. Next, the linearly polarized light 410 is
The 1-photon of the hawk 2 (which becomes an analyzer when viewed from the linearly polarized light 410) 52 is incident on it, but the polarizer 52 of 9.32 is more than the photon #i as shown in FIG. 1(g)! Since it is configured to transmit polarized light, the above-mentioned linear side ft410 can be used for that purpose without changing the plane of polarization. ! , the light passes through the second polarizer 52t and enters the plastic original fiber 2.

Next, the wavelength 0.
The manner in which visible light with a wavelength of 67 μm is converted into infrared light with a wavelength of 1.3 μm will be explained. In this case, the traveling direction of the light is in the negative direction of the z-axis. In FIG. 1(a), 451 is the output light of the plastic fiber 2, and the second polarizer 52 makes an angle of 45° with the negative direction of the X-axis as shown in xfl(g). It is converted into a straight line side light 452. Linear polarized light 45
2 is then incident on the second half-wave plate 62 for 0.67 μm, so that the polarization plane as shown in FIG. 1(f) makes an angle of 45° with the positive direction of the X-axis. It is converted into linearly polarized light 453. Next, the linearly polarized light 453 enters the second Faraday element 72, and the plane of polarization is rotated. However, since the direction of rotation of the plane of polarization in the 7Araday element is unrelated to the original traveling direction, the above-mentioned The polarization plane of the @line side light 453 is rotated 45 degrees counterclockwise when viewed from the positive sign direction of the two axes, and becomes linearly polarized light with a polarization plane parallel to the plane of paper 82 as shown in Figure m1 (h). 45
Converted to 4. Next, the linearly polarized light 454 enters the second polarizing beam splitter 92, but the $2 polarizing beam splitter 92 emits rim polarized light having a polarization plane in a direction 82 parallel to the plane of incidence, and the linear side - f455, is further reflected by the reflecting mirror 93, and becomes a non-amorphous medium LiN.
1 ps is incident on the resonator 121 containing 12 t-. In this resonator 121, by appropriately selecting the medium constituting the resonator and the phase matching conditions, visible light of 0.67 μm becomes excitation light, increasing the parameter IJ, and increasing the L3 μm.
Infrared light of 1.38 μm and visible light of excitation light fn 67 μm are all emitted. Next, the source 456 of these three wavelengths
first passes through the low-pass filter 13, and only the infrared light 457 with a wavelength of 3 μm and 1.383 μm is extracted, and then passes through the second high-pass filter 14, and infrared light with a wavelength of 1.30 μm is extracted. Only 458 and 9 lights are emitted. infrared light 4
The plane of polarization at 58 is parallel to the plane of the paper, as shown at 82.

In the l-th i#i1 beam splitter 91, linearly polarized light having a plane of polarization in a direction parallel to its incident plane is reflected, so the above-mentioned infrared light 459 is reflected by the first polarizing beam splitter 91. , enters the first Faraday element 71. In this case as well, the rotation direction of the polarization plane by the first 7-arrate element is unrelated to the original direction of travel, so the polarization plane of the linearly polarized light 459 rotates counterclockwise when viewed from the positive direction of the Z-axis. The polarization plane of the emitted light 46 of the first 7-Alade element 71 is rotated by 45 degrees, and the polarization plane of the light 46 is xtj@ as shown in FIG. 1(i).
It becomes linearly polarized light that makes an angle of 45° with the negative direction of . The emitted light 460 from the first 7-arrate element enters a half-wave plate 61 for a wavelength of 1.3 μrn, and is converted into linearly polarized light 461 as shown in FIG. 1(j). As mentioned above, the polarizer 51 of Vermilion 1 was designed to pass 7iA polarized light at 45 degrees with the positive direction of the X axis, so the linearly polarized light 461 mentioned above changes the direction of the 41 element plane. The light passes through the first polarizer 51 without any interference, becomes KM polarized light 62, and enters the quartz-based original fiber 1.

As explained in detail above, it is clear that infrared light with a wavelength of 1.3 μm and visible light with a wavelength of 0.67 μm are converted bilaterally.

Next, FIG. 2 shows a specific example of a communication system in which the bidirectional light wave conversion device according to the present invention is applied to an optical communication system including a plastic fiber. FIG. 2(a) shows the case where one quartz-based optical fiber and one plastic original fiber are used, and is almost the same as FIG. m1(a).

Next, FIG. 2(b) shows a case where there is one quartz-based optical fiber, but there are three original plastic fibers. In the figure, 3' is a central processing unit incorporating a bidirectional*e length conversion device, and signal transmission between the central processing units is performed using infrared light with a wavelength of 1.3 μm using a quartz optical fiber l'. Signal transmission between the terminal device @ 16 and the central processing unit 3' is carried out via the multiplexer/demultiplexer 15 using visible light with a wavelength of 0.67 μm using the plastic fiber 2. Note that 2 is a short-distance plastic fiber for transmitting signals between the central processing unit 3' and the multiplexing/demultiplexing device 15. In this way, bidirectional information transmission between the main line and the three terminal devices is possible.

The configuration of the present invention is not limited to the embodiments described above, and various modifications are possible. For example, in the present embodiment shown in FIG. 1, the polarization direction of the infrared original linear side 404 with a wavelength of 1.3 μm transmitted through the first polarizing beam splitter is set perpendicular to the plane of the paper, and the visible light beam with a wavelength of 067 μm is polarized light 4
The polarization direction of 54 was set to be parallel to the paper surface, but is it set by a polarizer? By changing the direction of the polarization plane and the direction of the magnetic field for the Faraday element, and by using an appropriate m-dimensional beam splitter, it is possible to reverse the polarization direction of the infrared light and the single polarization of the visible light. It doesn't matter if it's a relationship. Also, in this example, a reflecting mirror was used as the light direction changing means, but
Source fibers or other means for changing the direction of light may also be used. Furthermore, in this example, neither the silica-based optical fiber nor the glass optical fiber were polarization-maintaining type, but a polarization-maintaining original fiber was used, and the direction of its principal axis was set by Motoko Kami, as described above. A configuration in which the direction of the polarization plane coincides with the direction of the polarization plane may be used. At this time, the polarizer 51.

52 becomes unnecessary. Furthermore, if an appropriate element is used, the wavelength of infrared light and the wavelength of visible light may be set to different wavelengths.

Effects of the Invention As explained above, according to the present invention, infrared light at a transmission wavelength in a silica-based optical fiber and visible light at a transmission wavelength in a glass optical fiber can be easily transmitted bidirectionally. Since it can be converted, it is possible to expand the introduction of easy-to-handle plastic ft and 7-aibar fibers, which are easy to handle, for sending and receiving information between corporate offices and within and between banks. This has the effect of increasing the efficiency of using optical fibers.

[Brief explanation of the drawing]

FIG. 1(a) shows the U source of an embodiment of the bidirectional optical wavelength f conversion device according to the present invention, and FIG. Figure 1 (G) is a diagram showing the direction of polarization of Figure 3 is a configuration diagram of an example of conventional bidirectional information transmission. 1.1'...quartz optical fiber, 2.2', 2"...
・Glasstic optical fiber, 3... Long conversion of both quaternary #, 3'... Central processing equipment, 401-404,
458-462... Infrared light with wave length of 1.3 μm, 405
...Infrared light with a wavelength of 1.383 μm, 4o6-w length 1.
31Im infrared light and wave F and 1.383μm infrared light, 4
07... Visible light with wavelength 0.67μm and wavelength 21.9μm
Infrared light of m, 407', 408~411,451~
455... Visible light with a wavelength of 0.67 μm, 456...
Infrared light with R = 1.3 μm and wavelength 1.383 μtn and wavelength Q, 57. am visible light, 457-v length 1.3 μm,
Infrared light with R length 1.383 μm, 51°52...Polarizer, 61...Half-wave plate for wavelength 1.3 μIn, 62
・・・Half-wave plate for v length 0.67μ+n, 71.72・
...7 Alladay element, 81.82...Arrow indicating polarization direction, 91.92...Polarizing beam splitter, 93°94...Reflector, 10.../J & length 1.383 μm
11.12... Nonlinear medium bottomed from LiNbO3, 121... Common camera, 13... Low pass filter, 11'. ]4... High-pass transmission filter, 15... Multiplexer/demultiplexer, 1
6...Three terminal devices, 171, 172...Receiver,
181, 182...signal processing section, 191, J9
2...Half-clothed body 1 nose. Rotation゛shishi (a) 2nd illustration 3 wards

Claims (1)

[Claims] Using quartz-based optical fiber as the main signal transmission line,
In an optical communication system using a plastic optical fiber as a subscriber system signal transmission path, a first polarizer that converts infrared light emitted from the silica-based optical fiber into a first linearly polarized light, and a first half-wavelength a plate, a first polarization plane rotation element, and a first
a light source of locally oscillated light having a plane of polarization in the same direction as the linearly polarized light; and a first light source that transmits the first linearly polarized light having a specific plane of polarization of infrared light of a specific wavelength and reflects the locally oscillated light. a first polarizing beam splitter, a first frequency conversion component that introduces this plywood light and converts its frequency, a first high-pass filter, and a specific polarization direction of visible light of a specific wavelength obtained as an output thereof. The second one transmits only the linearly polarized light with , and reflects the others.
a polarization beam splitter, a second polarization plane rotation element,
A first light wavelength conversion path that includes a second half-wave plate and a second polarizer, and a first light wavelength conversion path that enters the plastic optical fiber; The light travels in the reverse direction through the second polarizer, the second half-wave plate, and the second polarization plane rotating element, becomes second linearly polarized light, and is reflected by the second polarizing beam splitter. , a second frequency conversion component composed of a resonator including a nonlinear medium, a low-pass transmission filter and a second high-pass transmission filter that pass the infrared light of a specific wavelength obtained at its output, and a light direction conversion component. means, is reflected by the first polarizing beam splitter, returns to the first optical wavelength conversion path, and further includes the first polarization plane rotating element, the first half-wave plate, and the first polarizing beam splitter. A second light wavelength conversion path is formed in which the light passes in the order of the polarizer and enters the silica-based optical fiber, and mutually converts the signal transmission wavelength in the silica-based optical fiber and the signal transmission wavelength in the plastic optical fiber. A bidirectional optical wavelength conversion device characterized by converting into.