JPS59204024A - Optical branching and coupling device - Google Patents

Abstract

PURPOSE:To obtain an optical accessor by which a crosstalk to an optical signal branching terminal from an optical signal inserting terminal is high, and also a passig loss of a main line light is low, by making the main line light incident to the first and the second polarization separating surface, and making an inserting light which is made incident to the second polarization separating surface from a direction different from the main line light coincide with an optical axis of the main line light. CONSTITUTION:For instance, a polarized beam splitter having a high polarization efficiency and a good transmittivity is adopted as polarization separating elements 113, 115, and they are placed and formed as one body so that dielectric multilayer film surfaces 114, 116 of two polarized beam splitters become parallel to each other. Four terminals each are placed on the end face of this element so that a P component from an incident terminal 101 is led to an optical signal branch terminal 103, and so that a P component from an optical signal inserting terminal 104 is led to an emitting terminal 102 by making an S component from the incident terminal 101 coincide with an optical axis. According to such a constitution, a crosstalk to the optical signal branch terminal 103 from the optical signal inserting terminal 104 can be made high, and also a passing loss to the emitting terminal from the incident terminal 101 can be made low.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an original signal branching and coupling device (original accessor) used in an optical signal transmission system such as optical communication.

Problems with the configuration of the conventional example Figure 1 shows an optical transmission system that uses a single signal as a medium. 11゜12 (l-1! This is the original signal path of the main line connecting the two stations. At each appropriate station 1 to 4, the signal of the main optical signal path βI" 2 is set as 15 as shown in Fig. 2. Alternatively, an optical transmission component having the function of inserting the optical transmission 3 into the main line in the signal path β4 is required.The present invention relates to an optical transmission component having the above function, The transmission parts will be called the former MAXEZA.

FIG. 3 shows a conventional source accessor. 101 is the source fiber of the main line that inputs light to the optical multiplexer! 11 and f,
102 is a terminal that outputs the signal from the main accessor to the main line Motofaino, 103 is a terminal that branches the light beam from the main line,
104 inserts an optical signal into the main line, :, :i, j
Ruru. Each terminal 101 to 104 is composed of an original fiber 106 serving as a transmission path and a collimator lens 106. Here, collimator lens 106rat, redundant fiber 1
It is used to convert the light emitted from the 05 into a crime beam, or to condense parallel beams in a source beam.

In FIG. 3, an optical element 1oγ, 108 having a function of totally reflecting a part of the light, such as a .-fmirror or an ND filter, is used to branch the light. A part of the original light emitted from the light input terminal 101 to the original accessor is transmitted to the optical element 10
7 and enters the original signal branch terminal 103. terminal 10
Of the light emitted from the optical element 10, the part that has passed through the optical elements 10'7 and 108 is emitted from the light output terminal 102. The light incident from the optical signal insertion terminal 104 is reflected by the optical element 108 , is superimposed with the optical axis aligned with that from the terminal 101 , and is emitted from the terminal 102 .

However, in FIG. 3, out of the light incident from the two terminals 104, only the collimator lens end face 1Q9 of the terminal 102. Alternatively, the source reflected from the original fiber mating end face of the nine-fiber connector located beyond that enters the original accessor again, and enters the collimator lens end face 11 of the terminal 101 or the original fiber mating end face of the original fiber connector beyond that. It is reflected by the optical element 10 and enters the optical accessor three times.
7 and causes crosstalk to the terminal 103, causing deterioration of the S/N. In order to reduce the amount of crosstalk, it is necessary to take difficult measures such as making the mating end face of the original fiber of the single fiber connector a surface with an inclination of more than the critical angle of the fiber with respect to + + an. In FIG. 3, 'M:, C, 2 on the way from the terminal 101 to the terminal 102
It passes through two optical elements 107 and 108, each of which reflects and misses a part of the optical element, so from terminal 101 to terminal 102.
The transmission loss essentially becomes large, about sdB or more, and the transmission path X++ is limited.

Purpose of the present invention (from the d11 signal insertion terminal to the original signal branch terminal -\'s θj Buddha 1tLi J'l: the arrow is 1°13<, and the trunk light passes) 1φI't- + a source with low loss The purpose is to provide access.

In the accessor of the present invention, the incident light is incident on the first polarization splitter surface V, and the polarization directions of the incident light are mutually (approximately perpendicular to the branching source and the main beam). Separate into the main light 'l!jl
t4, a second polarization splitting surface separate from the first 4Jnf source separation surface is incident on the second polarization separation surface, and insertion light is incident on the second polarization separation surface from a direction different from the main beam, and the insertion light and nl
By aligning the optical axes of the J trunk line.

The present invention is characterized in that the insertion light is superimposed on the optical path of the trunk light.

DESCRIPTION OF THE EMBODIMENTS FIG. 4 shows the original accessor according to the present invention, and the same parts as in FIG. 3 are given the same numbers.

In FIG. 4, 113 and 115 are polarization splitting elements, β1
is incident on the original accessor as a trunk light. The main beam β1 incident on the original accessor has a polarized light component (P component) polarized in parallel to the surface 114 obtained by reflection on the surface 114 having a polarization separation function of the polarization separation element 113, and a polarized light component (P component) obtained by being transmitted. It is polarized into a polarized light component (S component) having a polarization direction substantially perpendicular to the polarized light component. One polarized component (P component) of these two polarized potentials is guided to the optical signal branch ho 1.1 element 103 as a branched light β.

In addition, in FIG. 4, the other polarized light component (S component) of the two polarized lights separated is inputted into the second polarized light splitting element 115 as main light, and the polarized light splitting element 115 has a polarized light splitting function. The light is reflected or transmitted by a surface 116 having a shape of 1, and is guided from the single accessor to the original output terminal 102 to the main fiber. moreover.

The inserted light β4 incident on the second polarization separation element 115 from the terminal 104 for inserting the optical signal into the main line is transferred to the polarization separation element 1.
The original signal insertion terminal 104 is arranged so that the main light 11 from the input terminal 101 is guided to the output terminal 102 with its original axis coincident with the main light 11 by transmitting or reflecting it through the surface 116 having a polarization separation function of 15.

In this way, part of β1 is emitted as β3.

β1 and β4 can be stopped/reduced and emitted as β2.

FIG. 6 shows an original accessor according to an embodiment of the present invention, in which elements 113 and 114 are integrally formed. For example, the core fiber (105 in FIG. 1) of the main transmission line of the optical transmission system to which this embodiment is applied is 5.
0 μm, and an OH85 μm laser diode is used as the light source. Collimator lens (10 in Figure 1)
6) A single self-focusing lens is used so that the light beams emitted from the one-element fins become parallel rays at the end face of the self-focusing lens VC1 - and inside the original gold optical fiber that has passed through the polarization splitting elements 11.3 and 115. Make it possible to focus light on. In this embodiment, polarization beam splitters with high polarization efficiency and good transmittance at a wavelength of 0.85 μm are used as the polarization separation elements 113 and 115, and the dielectric multilayer blood removal 114, 116 of the two polarization beam splitters is were arranged so that they were parallel to each other and integrated. On the end face of this element, the P component from the input terminal 101 is connected to the original signal branch terminal 103.
Each of the four terminals is arranged so that the P component from the optical signal insertion terminal 104 is guided to the output terminal 102 with the optical axis aligned with the S component from the input terminal 101.

In order to increase the crosstalk loss caused by the end face reflection of the polarizing beam splitter, it is recommended to apply a single absorption paint to the lnA surface of the polarizing beam splitter other than the light receiving part and the light emitting part. Desirable crosstalk loss from the optical signal insertion terminal 104 to the optical signal branching terminal 103 in this embodiment will be explained using FIG. The P component from the original signal insertion terminal 104 is transmitted to the collimator lens end face 109 of the output terminal 102, the joint surface 110 between the collimator lens and the original fiber connector, or the original fiber mating end face of the original fiber connector (not shown). A portion of the light is reflected by the light emitting diode), etc., and enters the polarization separation element 115 again. This light β5
Since it is a P component, it is reflected by one surface 116, and the reflected light 7
1I6 returns to the original signal insertion end: f-104. Here, the polarization is completely separated at the surface 116, and the transmitted S component β7
For example, the light enters the polarization separation element 113 VC and is transmitted through one surface 114 , and the transmitted light 1 VB reaches the output terminal 101 . Of this element, 1j915 is reflected by the collimator lens end face 111 of the terminal 101 (or the original fiber mating end face (not shown) of the optical fiber connector located beyond the terminal 101), and becomes 1 circle, C11 element 1131/c is incident on this XL19.The 1:S component passes through 114 and proceeds '+o and stone:1j1' Of the light β9 that reaches the incident surface 114, completely 111I' ＋ )” minutes 11
P component β1. which is reflected without being reflected. ``L'': ””
It is tied to the j branch terminal 103. In the present invention, this light is the biggest cause of crosstalk loss from the optical No. 18 insertion terminal 104 to the original signal branch X:3:child 103.

(J:I! Because the element passes through the front element twice and the reflectance at the end face of the lens or optical fiber is about 1/10o, a crosstalk loss of 80 dB or more was achieved.

The light from the input terminal 101 that enters the polarization separation element 115 is not split on one side 116 and reaches the output terminal 10.
2, the transmission loss from the input terminal 101 to the output terminal 102 in the present invention can be made much lower than in the conventional example, and 3 dB can be achieved. The branch loss from the input terminal 101 to the original signal branch terminal 103 was 5 dB or less, and the coupling loss from the single signal insertion terminal 104 to the output terminal 102 was 5 dB or less.

Note that the method of arranging the polarization splitting elements 113g115 is as follows.
In addition to arranging the surfaces 114 and 116 having the polarization separation function parallel to each other as shown in the figure, various configurations having the same function can be considered. Depending on the arrangement of the surfaces 114 and 116 having one or two polarization separation functions, any polarization component can be used as a branch source or a main source. Input terminal 10
One polarization component, that is, the P component or the S component, which is polarized and separated at the plane 114 of the incident light β1 from 1, may be used as the entire trunk light, and the other polarization component, that is, the S fi1 or Hp component may be used as the branching source β5. It is possible to arbitrarily set whether the light A that passes through the two surfaces 114 and 116 is used as the main light beam, or whether it is reflected at the surfaces 114 and 116 and used as the main light beam.

In Fig. 5, the S component transmitted through one surface 114 is assumed to be the main light 1
The P component reflected by the surface 114 is used as branched light.

The P component of the inserted light β4 from the terminal 104 through the surface 116 is aligned with β1 and the optical axis and reflected, and the S component of β1 is superimposed with the S component of β1.
Is it all emitted as main light 12?V as shown in Figure 7
C, [rirl 1a, 116-t, (non-parallel toshi.

Let's make the source reflected at 116 from g-mani'-11'3 the trunk light, insert M, 1 in β4, and then combine the trunk light and 9 ゛ at 116 to create a passing field. The main light beam can also be set to β2/knee+a]. As shown in FIGS. 8 and 9, it is also possible to use the reflected P component at 1h4114 as the trunk & 1 tail, and the transmitted light S component as the branching source. And in Figure 8, as in Figure 7,
The main light is reflected by the surface 16, and the S component of the inserted light that has passed through the surface 116 is superimposed on the main light 12, and the main light 12 is emitted.
In the figure, as shown in FIG. 5, the transmitted light at the surface 116 and the reflected light of β4 are all main light beams β2.

As described above, in the present invention, the arrangement of the surfaces 114 and 116 as two branching sources and a main line source is used in a parallel configuration. Similar effects can be obtained by using other polarization splitting elements such as Niprism Boar. Ushita.

Integrating the polarization splitting elements 113 and 115 as shown in Figure 5 has the effect of preventing reflection at the end face of the polarization splitting element and completely preventing optical axis misalignment between the polarization splitting elements, improving the characteristics of the original accessor. You can improve.

Specifically, the optical fiber 105 and the collimator lens 106
The input/output terminal is not limited to a terminal consisting of a combination of the above, but any other configuration may be used as long as the input/output terminal can input parallel light beams. Note that the optical signal input terminal 104 directly connects the optical element to the polarization separation element 1 so that the incident light beam becomes a parallel beam.
The same effect can be obtained even if the end face of No. 15 is used. here,
If we use the polarized 1/&shi of a laser beam as the incident light, we can calculate the total value of one set of beams. It's ox, ``M:
, as the signal branch y1''h1 element 103, the polarization separation element 1
The same effect can be obtained by attaching a jt+ receiving element to the end face of 13.

Incidentally, the light emitted from the light output terminal 101 of the redundant accessor and the light incident from the terminal 104 are linearly polarized light having directions 11 and 1liIi orthogonal to each other.

When connecting multiple accessors, transmission of a predetermined optical accessor and the subsequent original accessor of the next stage i+
If J1 is 1, 1, the deflection direction of the beam that is incident on the next stage's original accessor is not completely random, and depending on the < +lli direction state, the main optical signal is The branching ratio at which the main accelerator branches into the main b' branch terminal and the output terminal changes. To prevent this, the first
Figure 0 (not shown). One dimension component of λ/4 root plate j is linearly polarized between the optical accessor 2Or and the next stage accessor 300.
Consolidation) It is preferable to arrange an element to form an L silane and lead it to the input terminal 101 of the main accessor 300 in the next stage.

-Also, A Iij VC between optical separation elements 11.3 and 115
By arranging the isolator 600i as shown in FIG. 11, one light beam is emitted from the output terminal 102 through the lens ψ)
14 surface or the original fiber connector, and element 11
3, the crosstalk from terminal 104 to terminal 103 can be further reduced. however,
In this case, it is necessary to adjust the arrangement angle of the separation plane by one angle by which the straight line fJnf, W; of the main light beam has its deflection direction rotated by the isolator 500.

Effects of the Invention According to the present invention, H7 from one optical signal insertion terminal to optical signal branching
It is possible to obtain a high-performance original accessor with extremely high 7-part loss and low transmission loss of main light.

[Brief explanation of the drawing]

Figure 1 is a schematic configuration diagram of the optical transmission system used in the first part of the optical accessor, Figure 2 is a diagram for explaining the function of the base accessor, and Figure 3 (shows the function of reflecting the base of the first part). FIG. 4 is a schematic diagram of a conventional source accessor using an optical element having the same structure. FIG. 4 is a diagram for explaining the configuration of the source accessor of the present invention, and FIG. , FIG. 6 is a diagram for explaining the crosstalk loss of the present invention, FIG. 7, FIG. 8,
FIG. 9 is a schematic configuration diagram of a source accessor according to another embodiment of the present invention. FIG. 1Q is a diagram in which a λ/4 plate is placed between two original accessors, and FIG. 11 is a diagram in which an isolator is placed between two polarization separation elements of the original accessor. 101...Terminal for inputting light from the main optical fiber to the original accessor, 102...Terminal for outputting light from the original accessor to the original fiber for the main line, 103...- Original signal branch terminal from the main line , 104...Original signal insertion terminal to main line, 105...Original fiber, 106...
Collimation lens, 113, 115...1λ
Mouth 1 element leaf element, 114, 116... 2) + 200... 1st stage base element, which has a polarization separation function.
300...Next stage former accessor, 400...
λ/4 plate. 500...Isolator, β1...Main light (
Incident light), β2...Main light (outgoing light), β3 ""
” Branch source. 14 -... Insertion light. Name of agent: Patent attorney Toshio Nakao and 1 other person
Figure 1 Figure 2 Figure 4 Figure 13 ↑14 fno4 61M @ Figure 7 J2 Figure 8 Figure 9 Figure 1!2

Claims (4)

[Claims] (1) The incident light is made incident on a first polarization separation surface, the incident light is separated into a branch source and a main light whose polarization directions are substantially orthogonal to each other, and the main light is separated from the first polarization separation surface. the second of
incident on the polarization separation plane. The insertion light is made incident on the second polarization separation surface from a direction different from that of the main light, and the optical axes of the insertion light and the main light are made to coincide, thereby superimposing the insertion light on the optical path of the main light. An optical branching/coupling device characterized by: (2) Incidence') i f, H Of the two polarized lights that are almost orthogonal to each other that are incident on the first polarization splitting surface, the polarized light that passes through the first polarization splitting surface is used as the trunk light or the branch source, and Self 2
2. The optical branching/coupling device according to claim 1, wherein the polarized light reflected by the first polarization splitting surface is used as the branching source or trunk light. (3) Inject the insertion light into the second polarization separation surface, reflect or transmit the insertion light on the second polarization separation surface, and
By aligning the original axes of the main light transmitted or reflected through the polarization separation surface of the main light and the inserted light after reflection or transmission, the insertion light is superimposed on the optical path of the main light. The optical branching/coupling device according to scope 1. (4) The optical branching/coupling device described in item 1 of the scope of Patent No. 51J, characterized in that the light is made unpolarized through an incident MZtλ/4 (λ: wavelength of incident light) plate.