JPS603605A - Optical branch - Google Patents

Abstract

PURPOSE:To obtain an information transmitting network at a low cost by constituting it by a mixing element for dividing equally an optical signal which has been made incident from one optical fiber into a branch bundle sticking tightly to the other end face, by utilizing a total reflection of many times in the inside. CONSTITUTION:A titled device is provided with a signal input/output terminal 10 whose constituting elements are a few optical fibers of a minute diameter and one large aperture optical fiber, a fiber 11 used for light emitting element for leading an output of a light emitting element to a mixing fiber 13, and a fiber 12 used for photodetector for leading an optical output which has transmitted through a mixing fiber 13, to a photodetector. When a signal is made incident to the mixing fiber 13 from one of the light fibers 11 for light emitting element serving as one element of the signal input/output terminal 10, a total reflection in the inside becomes asymmetrical with respect to the axis since the mixing fiber 13 is bent, therefore, said signal becomes uniform on the end face of a signal output/input terminal 14 side of the mixing fiber 13, and divided equally to plural terminal use fibers 15 having an equal diameter, which are stuck tightly to its face.

Description

Detailed Description of the Invention The present invention relates to an optical branch in which a small number of signal input/output terminals and a large number of signal input/output terminals are installed facing each other along the flow of optical signals. In addition to having the function of equally distributing the optical signals input in large numbers from the signal input terminals to all the terminals among the many signal output/input terminals, it also distributes the optical signals input in small numbers to all the terminals among the many signal output/input terminals. The feature is that efficiency is achieved by concentrating the signal input/output terminals at the output terminal.

Conventional optical branches can be divided into two types: transmission type and reflection type, and their typical structures are shown in FIG.

In the figure, a is an example of a transmissive type, and 1) is an example of a reflective type. In the figure, (1) is the input side branch bundle, +
2) &'! Mixing rod, (3) output 14 lIO
Branch handle, (4) is optical fiber, +51&'! The spacer (6) is the cross-sectional shape of the input side branch bundle (1) composed of the optical fiber (4) and the spacer (5) at a point near the bundle end.

(7) is the cross-sectional shape of the mixer rod, (8) is the reflective film (9
) vapor deposited mixing rod. Optical fiber (
4) are arranged radially around spacers having the same outer diameter as the fiber, and the outer diameter of the circle circumscribing the bundled end of the optical fiber (4) is the outer diameter of the mixing rod (2). Almost the same dimensions but somewhat smaller values.

Therefore, the optical signal incident from the optical fiber (4) constituting any input-side branch bundle (1) is not dissipated outside the mixing rod (2) and has an annular intensity distribution at the output end of the mixing rod (2). The light propagates with the same amount of energy and is efficiently and evenly distributed to the output side branch bundle (3). In this respect, it was an efficient light distribution element, but
For example, it is possible to convert the wavelength and input it from the output side branch bundle 13+, and to receive it with one or more light receiving elements connected to the input side branch bundle (1), but if you try to receive it with a small number of light receiving elements, the number of light receiving elements is small. It had to be said that it was an inefficient coupling element.

This invention improves the performance of the above-mentioned conventional device as a coupling element, thereby converting the output of a light emitting element connected to a large number of signal input/output terminals into the output of a light emitting element connected to a small number of signal input/output terminals. The aim is to reduce the cost of information transmission networks that use optical branches as components.

FIG. 2 is a block diagram of the optical section according to the first embodiment of the present invention. In the figure, the signal input/output terminal consists of a micro-diameter optical fiber and one large-diameter optical fiber that require 110 man-hours.
A light emitting element fiber made of 00 μm optical fiber is used to guide the output of the light emitting element to the mixing fiber described later, and a large diameter optical fiber is used to guide the light output transmitted through the a'atx mixing 7 eyeper to the light receiving element. Fiber for photodetector.

(In order to divide the output light of the 13161 light-emitting element fiber 0υ into the terminal fiber (I!9), which will be described later, in close contact with the other end face, and to divide the output light of the terminal fiber (2) into either of the terminal fibers, A4) A mixing fiber that serves to guide the light signal to the light receiving element fiber with a uniform intensity distribution. A signal input/output terminal in which terminal fiber α9 is bundled to lead to a terminal installed in a remote location, a-terminal fiber, OH'! signal input/signal input/output terminal, and a portion close to single fiber Q:1. , (Iη is the cross section of the mixing fiber. One ring is the cross section of the signal input/output terminal α. Since the device is configured in this way, the cross section of the mixing fiber is the cross section of the signal input/output terminal α. When a signal enters the mixing fiber 0 from one of the fibers αυ, the mixing fiber (I) is bent, so the total internal reflection becomes asymmetrical about the axis, so the end face of the mixing fiber 0 on the signal input/output terminal I side. , and is equally divided into a plurality of terminal fibers a!9 having the same diameter that are closely attached to that surface.On the other hand, when a signal enters the mixing fiber Q31 from the warm side of the terminal fiber a!

Mixing fiber (due to the action of 13, the intensity distribution of the signal light is uniform on the end face on the side of the signal input/output terminal α as described above), and the light emitting element fiber aυ is proportional to the size of the cross-sectional area.
The signal light is split into the light receiving element fiber Q2. Therefore, most of the signal light incident from any one of the terminal fibers (151) enters the light-receiving element fiber a2, thereby forming an efficient received signal transmission network.

A signal transmission network using this star coupler may give the illusion of an inefficient network for signals transmitted from the light emitting element fiber aυ. Moreover,
In actual operation, the light emitting element or the station containing the light emitting element connected to eye bar 0υ (for 0 light emitting element), this station is tentatively referred to as the master station, but this number should be small, 2 to 2. There are many. On the other hand, in this signal transmission network, the number of stations having light transmitting/receiving elements connected to the terminal fiber aQ, which we will call a slave station, is often as large as 8 to 32. When considering the number of stations that will be connected to the main station, use an expensive but high-output light-emitting element for the master station, and use an inexpensive light-emitting element for the slave stations, considering the large number of light-emitting elements to be used. If the output is low, this signal transmission network can be said to be efficient from an economical point of view.

The above discussion did not include the output of the light-emitting element and the minimum detectable light power of the receiving circuit including the light-receiving element, etc., but in the following, these specific numbers will be shown and the present invention will be explained. Explain that it is valid and realistic.

? Jf, Table 1 shows the light emitting output of a Mitsubishi Electric light emitting diode as a typical example of a light emitting element and a light receiving element, the reception width using a PIN photodiode, and the transmission of the light emitting diode to an optical fiber. It shows the combined light weight and power.

Table 1 Light emitting output of light emitting diode and Receiver minimum received power The modulation band for both the light emitting element and the receiver is 5.3MH.

That's all. The first and second rows are the outputs of the light emitting elements.

The third and fourth rows contain the receiver's maximum/JS received optical power.

The third line is for analog transmission; the fourth line is for digital transmission.

FIG. 3 shows the location where transmission loss occurs inside the optical branch according to the present invention whose arrangement of optical components is shown in detail in FIG. 2. In the figure, H is a light emitting diode whose light emission output is modulated by the signal to be transmitted, m is an optical connector for connecting the terminal fiber a field to an external fiber, and cl
υ is the external fiber connecting the slave station and this optical branch, C2
2 is a light-receiving element for converting the signal light transmitted from the slave station through the external fiber (2), optical connector 4, terminal fiber a! 9. mixing rod (13), and light-receiving element fiber a! The letters A to K in the figure are symbols for indicating the level of signal light at that location and the loss occurring at that location.

A is a component of the output of the light emitting diode that is focused by the coupling optical system and enters the optical fiber, which can be propagated over a long distance, and is the value in the first to second rows of Table 1.

B is the fiber Qυ for the light emitting element and the fiber side z for the light receiving element.
The main cause is microbending loss, which occurs when multiple optical fibers are bundled together, and propagating light enters the interface between the core and cladding at an angle greater than the critical angle to bend the optical fiber with a minute curvature. This is the loss during bundling, and the specific value for a quartz fiber with a core diameter of 50 μm is a center value of 0.2 dB and a standard deviation of dispersion of 0.2 dB.
It is about 1 dB. C is the interface between the medium with different refractive index, such as adhesive and void, existing between the light-emitting element fiber αυ or the light-receiving element fiber Q7J and the mixing rod side, and three types of optical components aυ, (IL Q3) D is the reflection or scattering loss that exists in the mixing rod Q31, and normally takes a value of about 0.1 dB. D is the absorption loss inside the mixing rod Q31, and as already explained, it makes the intensity distribution of the signal light at the output end face of the rod uniform. Therefore, it is a microbending loss caused by bending, and can be suppressed to about 0.1 dB if fluctuations at the output end face are allowed to about ±0.2 tlB of the center value.E is the cross section of the mixing rod Q3 and the terminal The cross-sectional areas of the fibers Q9 do not match, the individual cross-sectional shapes of the terminal fibers (151) are circular, so there are gaps even if they are packed close together so that their outer peripheries touch, and the terminal fibers (7)
1!19 consists of a core part that propagates light and a cladding part that has a low refractive index and acts only to cause total reflection at the boundary surface. Fiber a for bundling terminals with backing fraction loss and a core diameter/cladding diameter ratio of about 1.25, but laminated fibers! 9 number N=approximately 7 to 100 lines Te & Z 1 GlogN plus a value of approximately 3 to 6 dB.

Like C, F is reflection or scattering loss at the junction surface VC, and D is about 0.1 dB. G is the same loss during bundling as B, and has a value of about 0.2 clB. For H, we used a so-called step index type fiber with a Mikikung rod OJ and a terminal fiber [151] whose internal refractive index distribution is uniform in the core part 9 to equalize the distribution ratio, gradually reduce the splice loss, and type of external fiber υ In contrast, when connecting this step-index fiber with graded fiber, which has a wide transmission band and has become popular as a medium-distance transmission line, This is a loss caused by a difference in the allowable angle range of the propagating light.The refractive index distribution format is abbreviated as ql→a.
This will be referred to as the X conversion loss, and its value is approximately f, 6 dB. The average value for a PC type connector is 0.45 dB.

Now, the sum of the power or loss from 9 or more from A to 1 becomes the predetermined power exiting this optical branch, and its value is as follows.

With reference to Table 1, it will be understood that this value is at a sufficiently higher level than the minimum received optical power of the digital signal receiver, and is a branch suitable for this system.

In FIG. 3, the loss when the signal light propagates in the opposite direction to that described above is also indicated by an upward arrow. It shows according to the signal flow, and the engineering.

G, F, D, J, C, B. Compared to the rightward case in FIG. 3, the backing fraction loss of E has disappeared, and instead J has occurred due to the same cause, and K has occurred instead of A.

The main difference is the disappearance of H. First, it is clear that E disappears and J occurs by looking at the cross-sectional shape of the signal input/output terminal or input/output terminal near the junction surface with the mixing fiber α in FIG. 2. Next, it is natural that A disappears and K occurs, since we are considering the case of receiving signal light.
The specific value of
If the diameter of the fiber for the light-receiving element is made equal to or somewhat larger than the diameter of the mixing fiber .theta. moat, it is possible to make it approximately 3 dB.

The last ring is the point where H disappears in the leftward signal flow, but this is because inside the optical branch, all types of optical fibers on the way from receiving light at optical connector Qα to reaching light receiving element 4 are steps. It depends on being an index. The sum of the losses from I to K shown above and the minimum received signal of the receiver indicates the minimum level of the signal that can be detected as a signal by this optical branch, and the value is as follows.

Table 3 Comparing this value with the first and second rows of Table 1, the minimum optical power that can be received by the optical branch with the terminal fiber shows that the slave station can use the fiber with a core diameter of 50 μm or more and a numerical aperture of 0.2 or more. It can be seen that analog signals can be transmitted with a sufficiently high S/N ratio by connecting everything from the light emitting element to the optical branch according to the present invention. In addition, the first and second rows of Table 1
Since the row 1 indicates the center value of the peak power of the LED, it is likely that there will be cases where the center value is not reached when a large number of devices are produced. This signal flow is achieved by ensuring a sufficient S/N ratio or code error rate even when a large number of terminals are connected, and it can be said to be an efficient optical branching from an economic point of view.

FIG. 4 is a conceptual diagram of an optical component showing a second embodiment of optical branching according to the present invention. The difference from the embodiment shown in Fig. 2 is that the light emitting element fiber a constituting the signal input/output terminal
By making υ and the thickness of the light-receiving element fiber Qa almost equal,
As in the case of the first embodiment described above, the power of the rightward signal light flow in FIG. This optical branch can also be used to transmit analog signals.

FIG. 5 is a schematic diagram of a line for explaining line loss in the embodiment of FIG. 4. The alphabet in the diagram is the first
Similarly to the explanation of the embodiment, this is a symbol indicating the location where the loss occurs. (II is a diameter of 110 μm or more.

For LEDs, a fiber with a numerical aperture of 0.2 or more is installed close to the light emitting part. From Table 1, the power A' of the signal light transmitted into the fiber is -6 (lBm). αυ is the light emitting element. (This is a light-emitting element fiber made of a large-diameter optical fiber with a core diameter equal to or larger than that of the fiber installed in 11, and here the core diameter is 110 μm.

A fiber with a step index type refractive index distribution with a cladding diameter of 15011 m + numerical aperture of 02 is used.

B' is the microbedding loss that occurs when the optical fibers αυ for light emitting devices are bundled, and its specific value)'!
There is 0.2 dBf / °'& 1 luminous phase] The optical fiber is a reflection or scattering loss that occurs when the mixing fibers are bundled and joined together, and its specific value &X 0
．． It is 1 dB. 03 Humming fiber 91
As shown schematically in the figure, it has a bent shape, and DI is the loss caused by bending, and its specific value &'! It is 0.1 dB. E' is the backing fraction loss, and its specific value is α in Figure 4.
In the case of the cross-sectional shape shown with the symbol .about.0, it is approximately 16 dB when the core diameter/cladding diameter ratio of the individual terminal fiber Q is 1.25.

F' is a scattering or reflection loss similar to C', and its specific value is 0.1 dB. This is a loss due to bundling similar to QlhgoB', and its specific value is 0.2 dB. H' is the S->Gl conversion loss caused by the difference in the refractive index distribution between the optical fiber αυ, (I3 and α4) inside the optical branch and the external fiber (2+1), and its specific value &X1
．． It is 6dB. ■' is a connector loss, and its specific value is 0.45 dB. From what has been said above, the fourth
Table 4 shows each level of the lower line of the embodiment shown in the figure.

Table 4 Optical level of the downstream line (insertion of 16 branches) This value is sufficiently larger than the third and fourth rows of Table 1 to make the optical branch as shown in Figure 4. It can be seen that the configuration is suitable for both digital signal transmission and analog signal transmission.

Now let me explain about the uplink level.

The difference between the upper line and the downlink is that first, the knocking fraction loss E' disappears, and in its place, the knocking fraction loss J' occurs on the opposite end of the mixing fiber. That's true.

Second, the S->GI conversion loss H' at the optical connector (a) has disappeared. The size of J' is
If the relationship between the cross-sectional shapes of the signal input/output terminal αQ and the mixing fiber Q4 is as shown in FIG.
It becomes 5dB. Since the numerical value of 5 is the same as shown above, the optical level of the upper line can be determined as shown in Table 5.

Table 5 Optical level of the upper line Comparing this value with the first and second rows of Table 1, all light emitting elements have a sufficiently high output compared to the minimum receivable optical power of the optical branch. Therefore, it can be seen that the embodiment of FIG. 4 can establish an uplink for both analog signals and digital signals.

FIG. 6 is a block diagram of the optical branching according to the present invention explained above. In the figure, (c) is an optical transmitter that includes a plurality of light emitting elements. (J41 is a light-emitting element cord whose core wire is a light-emitting element fiber (A), (C) is a light-receiving element cord whose core wire is a light-receiving element fiber A3, and (C) is a cord of the above two cords tied together. A flange with built-in fiber handle, (c) is a mixing fiber cord with mixing fiber a3' as the core wire, (20 and CI'
l is a flange attached to both ends of the mixing fiber cord, C3υ is a terminal cord whose core wire is terminal fiber α9, C3 [# is a flange that incorporates a fiber bundle that bundles the core wires of the terminal cord C1l+, oat
The ferrule attached to the terminal side of the i-terminal cord 0υ, r33 is the receptacle that is a component of the optical connector (2), and (b) is the optical receiver that is attached to the optical element cord (c) and has a built-in light receiving element. (2) is the casing. If the device is configured as shown in the figure, the light emitted from the optical transmitter (c) will be transmitted through the light emitting element code CJ41. The mixing fiber cord connects the terminal cord Ov to the trans-tele receptacle (to) and is input to the external fiber Qυ connected thereto. On the other hand, the optical signal input from the external 7 fiber Cal+ to the optical receiver via the receptacle (to), the terminal cord C311, the MIKI 1 single fiber cord (2), and the light receiving element cord (c) is is converted into an electrical signal.

The point to keep in mind in the configuration of FIG. 6 is that the radius of curvature of the bending part of the mixing fiber cord (7), for example, is the intensity distribution of the signal light incident from the flange Qθ side. The goal is to make it a small enough value to make it uniform at the output end on the side of flange Cl71, but 2
．． The second point to keep in mind is that the radius of curvature of the bent portion should not be below a certain limit. If this limit value is exceeded, even if the fiber does not break immediately after being bent, minute scratches existing on the surface of the mixing fiber may grow due to internal stress after being left for a long time, leading to breakage. The above limit values vary depending on the manufacturing conditions of the mixing fiber Q3, the surface retention conditions, and the storage environment conditions after bending. When the core is made of silicone resin or polyurethane, the value has the following relationship with the diameter of the mixing fiber a3.

j? nT=517.1-24.66.1/n(40, υ
Sa/ζ) Here, T is the lifetime, d is the diameter of the mixing fiber a3, and ζ is the critical radius of curvature. In the embodiment shown in FIG. 4, since d is 0.4 mm, the critical radius of curvature ζ that provides the life T=10 years is in the order of 28.

FIG. 7 is a diagram showing the arrangement of optical components in a third embodiment of the optical branching system according to the present invention. This embodiment differs from the second embodiment shown in FIG. 4 in the following three points. The first is that the mixing fiber 03 is installed in a substantially straight line. The second method is to arrange the fibers 0υ and a, which serve two purposes and make up the signal input/output terminal θ1, to have the same diameter and arrange them in a close-packed arrangement. The circle shown (
(to) is concentric with the mixing fiber 03, but it is also made extremely large as will be described later. The third is the terminal fiber a! which constitutes the signal input/output terminal a4. 1
9 are arranged in a ring shape on the circumference with the center extending from the axis of the mixing fiber θ. Circumference O of the ring
? ) has almost the same diameter as the mixing fiber 03, but in Figure 2, the diameter of the mixing fiber 03 is also drawn in bold because it would be difficult to see if they were drawn overlapping each other. This third embodiment is effective.

It will become clear if we explain the transmission loss at each part in the same way as shown in the previous two examples, but before that, we should explain that the incidence is biased at the entrance-side joint surface facing the mixing rod, which is the basis for evaluating the transmission loss. Light is emitted from the light emitting element fiber aυ #J II! Describe what kind of distribution it has on the I m plane.

Figure 8 shows the dependence of the radial distance of the mixing fiber α on the output light intensity on the side of the signal input/output terminal α4 when the optical fiber is eccentrically attached to the side of the signal input/output terminal shown in Figure 1. . In the figure, the horizontal axis represents the radial distance, and the vertical axis represents the intensity of light that enters the fiber when an optical fiber having the same dimensions and the same refractive index distribution as the input side optical fiber is brought into close contact with the output side end face. It is something that The diameter of the core of the mixing fiber Q3 is 400 μm, and the diameters of the input and output optical fibers are 50 μm. The input position of the input side optical fiber is 155 μm from the center of the mixing fiber (I3), which simulates the arrangement of 10 terminal cores (11) lined up in an annular shape, just like the cross section in Figure 7. Now, what is clear from Fig. 8 is that the distribution of the transmitted light intensity at the output end of the mixing rod (I) in an eccentric arrangement like the cross section shown in Fig. 7 is circular.

A feature of this embodiment is that optical signals can be distributed efficiently if the terminal fibers α forming the input/output terminal a4 are arranged to form a ring of approximately the same size as the ring coming from the transmitted light. . The measured values in FIG. 8 show that the excess loss is low, ranging from 3 dB to 3.5 dB. The measured values in Figure 8 are for signal input/output terminal a0 and signal input/output terminal I.
This is an example in which the light-emitting element fiber aυ and the light-receiving element fiber aa that constitute the light-emitting element fiber aυ and the light-receiving element fiber aa have the same diameter. Signal input/output terminal a when fixed at a position 155 μm from the center and enlarged as in Figure 8.
4 indicates the amount of increase in the optical signal received by the terminal fiber a4.
, *'o-c''', a・'"#"i'-M""#'"'
m-77''"11 The signal is increased to a range three times the diameter of the terminal fiber, and the amount of increase is the same as when the diameters of the light emitting element fiber and the terminal fiber of the same two dimensions are made equal. It can be seen that the increase is 6 dB.

Figure 10 shows the mixing fiber 0 and the light-emitting element fiber αυ in the example of Figure 1, in which the above study results have been determined.
The relationship between the terminal fiber a9 and the mixing fiber a3
It is shown as a figure projected onto a plane perpendicular to the central axis of . In the figure, αυ is the fiber for the light emitting device as in the previous symbols, and the double circle φ is to distinguish the core part and the cladding part. a
A is the fiber for the light-receiving element, and the double circle is the core portion and cladding portion. 05t! In the terminal fiber, the double circle is the core part and the cladding part. This is the core part of the α-tension mixing fiber, and the cladding part is (to). - is a circle located at the center of the fiber for light emitting element, light receiving element, and terminal. It will be clear from the above description that the optical levels of the upper multi-line and lower p-line in the embodiment of FIG. 10 are as shown in Table 6. Note that the symbols in Table 1 indicate the locations where loss occurs and are the same as in the second embodiment shown in FIG. It should be noted, however, that a packing/fraction loss of -2.5 dB is added to the input side end face of the A-level sheamixing fiber, which is different from the embodiment shown in FIG.

Table 6 Optical levels of lower multiple lines and upstream lines in the third embodiment (in case of 10 branches) In this table, the third embodiment in Fig. 7 is the second embodiment in Fig. 4. Since the number of downlinks is established with a larger margin than the above, it can be evaluated that the practical value has become even higher. In addition, the 6th
J' in the table = 6.18dB and J' in Table 5 = 8.5dB
The difference is between the light receiving element fiber 4 and the mixing fiber a.
In addition to the difference in the diameter ratio with 3, as shown in FIG.
This is because the transmitted light is distributed annularly and is efficiently captured by the light-receiving element fiber.

In addition, in the above explanation, two fibers for two light-emitting elements and one fiber for a light-receiving element have been explained, but many services are required from the master station to the slave station, such as urban TV broadcasting. Of course, in some cases, the requirements can be met by increasing the number of light emitting element fibers and using means such as wavelength multiplexing. However, in general, optoelectronic semiconductor devices (tts) have a high failure rate because they are operated with concentrated current or at a high reverse voltage compared to other passive electrical components. It may be better to emphasize the redundancy of multiple light emitting element fibers and the light emitting elements connected thereto as a backup for failures than to emphasize the diversity of services through multiplexing.

In the embodiment shown in Fig. 6, the optical transmitter (2) and the receiver (product) are housed in the housing can, but the fact that no active element is included means that the signal using the optical branching by this emission aA is It can be easily inferred that this is the basis for increasing the reliability of the transmission network. Optical branching emphasizing this point is as shown in FIG. 11.

In the above description, only light emitting diodes were taken up as the nine light emitting elements. In addition, only the PIN-type photodiode has been described as a light-receiving element. However, these references were only made to prove that the same line holds true even when such inexpensive elements are used, such as high-output laser diodes.

Needless to say, an avalanche photodiode with a low minimum receivable optical power can be used. However, it is well known that when using a laser diode, some measures are required, such as the purity of the oscillation spectrum being too high or the need to superimpose a high frequency signal.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of a conventional optical star coupler. FIG. 2 is a diagram showing the arrangement of optical components showing the first embodiment of the optical branching according to the present invention, FIG. 3 is a diagram showing the location where loss occurs in the first embodiment, and FIG. 4 is a diagram showing the location of the loss in the first embodiment. 2nd related to
FIG. 5 is a diagram showing the location where loss occurs in the second embodiment. FIG. 6 is a diagram showing the actual configuration of the optical branch described above. FIG. 8 is a diagram showing the arrangement of optical components in the third embodiment of the present invention, and FIG. A diagram showing the relationship between the signal increase amount and the ratio of the diameter of the light emitting element fiber and the diameter of the terminal fiber in the third embodiment V, and FIG. 10 clearly shows the cross-sectional shape of each fiber in the third embodiment. Mixing fiber 03 for
) is a view projected onto a plane perpendicular to the optical axis of the lens. FIG. 11 is a diagram showing an example in which an active element such as an optical transceiver is not included within the optical branch. In the figure, in the vagina, (1) is the input side branch bundle, (2) is the mixing rod, (3) is the output side branch bundle, +4
18! Optical fiber, (5) is a spacer, (cross section of 6m branch bundle, '(71tX cross section of mixing fiber, +a+t'z mixing rod with anti-i film,
(9) is anti'Mk, Q (I is the signal input/output terminal, (I
ll is the fiber for the light emitting element, (lη is the fiber for the light receiving element)
Iba, Q:H! mixing fiber. ALMA signal input/output terminal, fiber for AETRS terminal,
The cross section of the tuu'z signal input/output terminal, aη is the cross section of the mixing fiber, the cross section of the Qlt signal input/output terminal, a
rm light emitting diode, C1fJ is optical connector, cll
)G! external fiber. (2) is a light receiving element, (23t'z optical transmitter, C4) is a code for a light emitting element, (C) is a code for a light receiving element, (A), 00, (2) and c3IJ are one or more fibers. flange for fixing them to each other, @hamikikung fiber cord, cord for C311 & lA end, C32 & Z
Ferrule, 03+ is optical connector receptacle, (2
) is the optical receiver, (c) is the housing, @ is the circumscribed circle of the light-emitting element fiber and the light-receiving element fiber, 07) t, 'z
The circumcircle of the terminal fiber, (to) is the circle on which the centers of the terminal fiber, the light-emitting element fiber, and the light-receiving element fiber are located, ((1!'! This is the circle indicating the outer circumference of the cladding of the mixing fiber. Note that the same or equivalent parts in Figure 2 are indicated with the same reference numerals. Agent Masuo Oiwa Figure 1a Figure 1bl! 1 - Figure 7 Radial distance (pm) 2 2.5 3 3. 5 Figure 10

Claims (1)

[Claims] ■ A first branch bundle having an end where a plurality of optical fibers are bundled and a dispersed end where a plurality of optical fibers are not bundled. A second branch bundle configured using a different number of optical fibers from the first branch bundle is brought into close contact with two opposing end surfaces of the first and second branch bundles. It is composed of a mixing element that equally divides the optical signal incident on one optical fiber of the branch bundle closely attached to one end face into the branch bundle closely attached to the other end face by utilizing multiple internal total reflections. Optical bifurcation characterized by: (2) The optical branching according to claim (1), characterized in that a step index type optical fiber is used as the mixing element and is arranged in a meandering manner. (The optical branching according to claim (1), wherein the core diameter of one of the optical fibers constituting the 31 m2 branching bundle is made larger than that of the other optical fibers. (4) Optical branching according to claim 111, characterized in that the optical fibers constituting the first branching bundle and the second branching bundle are arranged in an annular shape. (5) First branching Optical branching according to claim (4), characterized in that the ratio of the core diameter of the optical fibers constituting the second branch bundle to the core diameter of the optical fibers constituting the bundle is 2.5 or more. (6) Claim No. 1 characterized in that the number of optical fibers constituting the first branch bundle is 10, and the number of optical fibers constituting the second branch bundle is 3. ) Optical branching described in section.