JP2006349815A - Optical communication device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical communication device which can maintain high performance by performing highly accurate positioning processing relating to the light from an LD at all times or at arbitrary timing even while maintaining a high quantity of light of a signal light used for communication at a more low cost, and to provide the optical communication device which can be constituted at low costs. <P>SOLUTION: The optical communication device comprises: a light source; an optical fiber which is constituted of a core and clad, having an incident end face to which the light from the light source is made to incident, transmitting the light made incident to the core in the incident end face; a detecting means which detects a light quantity of the light made incident to the area other than the core in the incident end face; a moving means which moves a beam spot position on the incident end face; and a control means which controls the moving means by negative feedback control so that a detected light quantity is minimized. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a configuration of an optical communication apparatus that performs optical communication using light emitted from a semiconductor laser (hereinafter referred to as LD).

  An optical communication device is a device for transmitting light emitted from an LD and modulated by information to an optical fiber, and is composed of an optical component such as an LD, a lens for condensing light from the LD, and an optical fiber. The In an optical communication device used as an optical network unit (ONU) that draws an optical fiber into a subscriber premises, in general, in order to support bidirectional communication in which transmission / reception is performed using a single optical fiber, The communication apparatus further includes a light receiving unit, a WDM (Wavelength Division Multiplex) filter for separating light of different wavelengths, and the like.

  In the optical communication apparatus as described above, since the signal light from the LD is transmitted / received via the optical fiber, the signal light needs to be incident on the core on the incident end face of the optical fiber with high accuracy. That is, when assembling the optical communication device, it is necessary to perform positioning (initial positioning) of the light irradiated from the LD with respect to the incident position in the optical fiber with high accuracy. Even after the initial positioning, each optical component such as an LD or an optical fiber is fixed, the deformation of the component due to processing such as adhesive shrinkage or welding, etc., and the performance of each component over time There is a risk that unintended misalignment may occur due to a change or the like. Therefore, the present applicant has proposed an optical communication apparatus as described in Patent Document 1 in order to cope with the unintended misalignment.

JP 2003-338895 A

  In the optical communication device disclosed in Patent Document 1, a part of the light guided into the core is changed to a fiber while periodically changing the beam spot forming position of the light emitted from the light source at a predetermined frequency in a predetermined direction. It is taken out of the optical fiber by an optical branching means such as a coupler. The position of the light at the incident end face of the optical fiber (that is, the position of the beam spot formed at the incident end face) is utilized by utilizing the intensity of the extracted light as the beam spot forming position approaches the core center. Negative feedback is controlled so as to go to the core center. In the text, wobbling refers to periodically changing light emitted from a light source in a predetermined direction at a predetermined frequency.

  According to the optical communication device disclosed in Patent Document 1, not only initial positioning at the time of assembling the device but also positioning can be performed constantly or at an arbitrary timing even during execution of optical communication. Therefore, it is possible to effectively avoid the influence due to unintended misalignment due to deformation of parts or changes with time when each optical part is fixed.

  However, in the configuration of the optical communication apparatus, a part of the light guided into the core is taken out of the optical fiber and used for negative feedback control. For this reason, the amount of light as signal light used for optical communication is slightly reduced. Further, it has been found that the light branching means for taking out part of the light is expensive and leads to an increase in the cost of the entire apparatus. Therefore, further improvement of the optical communication device is desired.

  In view of the above circumstances, the present invention performs high-precision positioning processing on the light from the LD at any time or at any timing while maintaining a high amount of signal light used for optical communication. An object of the present invention is to provide an optical communication apparatus that can maintain the above-described characteristics and can be configured at a lower cost.

  In order to achieve the above object, an optical communication apparatus according to the present invention includes a light source, a core, and a cladding, has an incident end face on which light from the light source is incident, and transmits the light incident on the core at the incident end face. An optical fiber, a detecting means for detecting the amount of light incident on a region other than the core on the incident end face, a moving means for moving the position of the beam spot on the incident end face, and a moving means so that the detected light quantity becomes a minimum value. And a control means for performing negative feedback control.

  According to the first aspect of the present invention, positioning of the light from the LD is performed based on the amount of light incident on the region other than the core of the optical fiber. Therefore, the positioning can be performed without impairing the amount of light emitted from the light source. In addition, the control means performs negative feedback control so that the beam spot forming position on the incident end face of the optical fiber is directed toward the core center, so that not only initial positioning but also positioning at any time or at any timing is possible. Therefore, it is possible to maintain the high performance of the apparatus while avoiding the influence of environmental changes and changes with time. Furthermore, since positioning is performed by using light incident on a region other than the core, it is not necessary to provide optical branching means such as a fiber coupler inside the optical fiber, and an inexpensive apparatus is provided.

  According to the second aspect of the present invention, it is possible to further include a light transmission means that is integrally formed on the circumferential surface of the optical fiber and that transmits the light incident on the area other than the core on the incident end face to the detection means. Thus, by integrally forming the light transmission means on the surface of the optical fiber, it becomes possible to more reliably guide the light incident on the area other than the core to the detection means.

More specifically, the light transmission means has a first end face that is in the same plane as the incident end face, and a second end face that is located on the opposite side of the first end face. It can comprise as a translucent cylindrical member to coat | cover. In this case, assuming that the refractive index of the cylindrical member is n1 and the refractive index of the cladding is n2, the refractive index n1 and the refractive index n2 are the following conditions (1),
n2 ≦ n1 (1)
(Claim 3).

More specifically, the cylindrical member and the clad are bonded with an adhesive having a refractive index nc, and the refractive index nc is determined by the following condition (2),
n2 ≦ nc ≦ n1 (2)
Meet.

  When the light transmission means as described above is used, the detection means can be configured to have a donut-shaped light receiving portion in which the light receiving surface is in contact with the entire second end surface. ).

  According to the sixth aspect of the present invention, it is desirable that the cylindrical member has a reflective film coated on the circumferential surface. Thereby, there is no possibility of light leaking in the process of transmitting the cylindrical member, and positioning with higher accuracy becomes possible.

  The detection means has a light receiving portion disposed on a surface substantially parallel to the optical axis of the optical fiber, and the second end surface is inclined at a predetermined angle with respect to the optical axis of the optical fiber. The light may be configured as a reflecting surface that guides light incident on the end face of the light to the light receiving unit. It is desirable that a film for increasing the reflectance is deposited on the second end face. The light receiving portion of the detecting means can be disposed on a surface substantially parallel to the optical axis of the optical fiber. The light receiving portion is joined to the cylindrical member via a transparent material having a refractive index equal to or higher than that of the cylindrical member.

  The cylindrical member can be provided with a function of protecting the optical fiber (claim 11). For example, a capillary is assumed as the cylindrical member.

  In addition, the light transmission means may have a film having a higher reflectance than that of the core disposed in a region other than the core on the incident end face. In this case, the detection means has a light receiving portion in the optical path of the light so as to receive the light reflected by the region other than the core on the incident end face.

  According to a thirteenth aspect of the present invention, it is desirable that the incident end face is inclined with respect to the optical axis of the optical fiber.

  Further, as the moving means, by moving the condenser lens in a direction orthogonal to the optical axis of the lens, or by driving each optical component such as a light source in a direction orthogonal to the straight light traveling direction, The spot may be moved on the incident end face. In addition, the moving means may include a transmission type deflection member between the light source and the optical fiber, and the position of the beam spot may be moved by deflecting the light by the transmission type deflection member. Item 16).

  According to the invention described in claim 17, the moving means can be moved while periodically changing the position of the beam spot in a predetermined direction. Specifically, since the light emitted from the light source is modulated by information, the moving means slightly changes the position of the beam spot at a predetermined frequency lower than the frequency of the information transmission band by the light ( Claim 18).

  In addition, as said transmissive | pervious deflection | deviation member, the vertex angle variable prism which can change an vertex angle is illustrated (Claim 22).

  With the optical communication apparatus having the above configuration, the negative feedback control by the control means can be performed simultaneously with the transmission of the light modulated by the information (claim 23).

  As described above, according to the present invention, by performing negative feedback control based on the amount of light incident on the optical fiber other than the core, while maintaining a high amount of signal light used for optical communication, Provided is an optical communication apparatus capable of maintaining high performance by executing highly accurate positioning processing relating to light from an LD at any time or at an arbitrary timing.

  Furthermore, by adopting a configuration that does not require the optical branching means, which is an essential component in the conventional optical communication device, the optical communication device according to the present invention can be configured at low cost.

  FIG. 1 is a diagram illustrating a configuration of an optical communication device 100 as a first embodiment of the present invention. The optical communication device 100 is used as an ONU that draws optical fiber communication into a subscriber premises. For example, the optical communication device 100 is configured to transmit a wavelength of 1.3 μm as an upstream signal and receive a signal of 1.5 μm as a downstream signal using a single optical fiber, and is compatible with bidirectional WDM transmission. It is a communication device. The optical communication device 100 according to the first embodiment includes an LD, a condenser lens 2, an optical fiber unit 10a, a controller 7, and an actuator 8.

  FIG. 2 is an enlarged view showing the optical fiber portion 10a. As shown in FIGS. 1 and 2, the optical fiber portion 10a has an optical fiber 3 comprising a core 31 and a clad 32, a hollow portion, and an adhesive layer (hereinafter simply referred to as an adhesive layer) c in the hollow portion. A cylindrical capillary 4 to which an optical fiber 3 is fitted, a light receiving portion 5 and a reflective film 6. That is, the optical fiber portion 10 a is configured as a multilayer structure with the core 31 as the center. The optical fiber portion 10 a has a first end surface 11 and a second end surface 12. The first end face 11 is also an incident end face on which light emitted from the LD is incident. The second end surface 12 is an end surface of the capillary 4 opposite to the first end surface. That is, the capillary 4 is designed to be shorter than the entire length of the optical fiber 3 and mainly protects the optical fiber 3 fitted in a predetermined range from the first end face 11.

The optical fiber portion 10a is configured so that each refractive index satisfies the following condition (1), where n1 is the refractive index of the capillary 4 and n2 is the refractive index of the cladding 32.
n2 ≦ n1 (1)

Further, assuming that the refractive index of the adhesive layer c is nc, the refractive indexes n1, n2, and nc are configured to satisfy the following condition (2).
n2 ≦ nc ≦ n1 (2)

  In the present embodiment, n1 is set to 1.494, n2 is set to 1.460, and nc is set to 1.494. That is, n2 <nc = n1, and both the conditions (1) and (2) are satisfied.

If the refractive index of the core 31 is n3, in the present embodiment, n3 is set to 1.464, and the optical fiber portion 10a further satisfies the following condition (3) due to the properties of the optical fiber.
n2 <n3 (3)

  The light receiving unit 5 is attached in a state where the light receiving surface is in contact with the second end surface 12. Here, as described above, the second end face 12 is only the end face of the capillary 4, and the optical fiber 3 extends from the center. Accordingly, as shown in FIG. 2, the light receiving portion 5 of the first embodiment is formed in a donut shape having a through hole having a diameter substantially the same as that of the optical fiber at the center portion. The reflective film 6 is provided on substantially the entire surface of the capillary 4 other than the first end surface 11 and the second end surface 12 (hereinafter referred to as a circumferential surface).

  In an optical communication apparatus that is actually used, the incident angle at the optical fiber 3 of the light beam output from the LD and incident on the optical fiber 3 via the condenser lens 2 is extremely small. However, in FIG. 1, the incident angle is shown larger than the actual angle for convenience of explanation.

  In the optical communication device 100 shown in FIG. 1, the first end surface 11 of the optical fiber 3 is cut at a surface other than the surface orthogonal to the optical axis of the optical fiber 3. In FIG. 1, the optical fiber 3 is shown as a cross-sectional shape on a plane including the optical axis of the optical fiber 3. In the present specification, the plane including the optical axis of the optical fiber 3 includes the optical axis of the optical fiber 3 and the plane perpendicular to the optical axis of the optical fiber 3 unless otherwise specified. A plane in which the angle formed by the end face 11 is defined is limited.

  In the optical communication apparatus 100, the optical fiber 3 is designed so that the optical axis of the optical fiber 3 is inclined at a predetermined angle with respect to the optical axis of the condenser lens 2 in consideration of the refraction phenomenon at the first end surface 11. It is arranged. That is, the optical communication device 100 is configured to reflect in a direction different from the incident direction when the light emitted from the LD is reflected by the first end surface 11. As a result, a phenomenon in which light irradiated from the LD and incident via the condenser lens 2 is reflected by the first end surface 11 and returns to the side where the LD is present, and the output of the LD is adjusted by the phenomenon. Control) effectively prevents the circuit from malfunctioning.

  During optical communication, light (signal light) modulated by a communication control unit (not shown) and emitted from the LD converges on the first end surface 11 of the optical fiber unit 10a via the condenser lens 2 to form a beam spot. To do. Then, the light transmitted through the core 31 is irradiated toward another optical communication device to be communicated.

  Hereinafter, a configuration for positioning the beam spot formed on the first end face 11 of the light irradiated from the LD in the optical communication apparatus 100, which is the main feature of the present invention, toward the core center will be described in detail.

  First, the optical path of the light irradiated from the LD in the optical fiber portion 10a will be described. In addition, as above-mentioned, in this embodiment, the 1st end surface 11 is cut | disconnected by surfaces other than the surface orthogonal to the optical axis of the optical fiber part 10a. Moreover, the optical fiber 3 is disposed so that the optical axis of the optical fiber 3 is inclined at a predetermined angle with respect to the optical axis of the condenser lens 2. Therefore, when the light emitted from the condenser lens 2 and incident on the first end surface 11 is considered as a bundle of a plurality of light beams, the incident angles of the light beams when the first end surface 11 is incident are different. However, the angle formed between the first end surface 11 assumed in the present embodiment and a surface orthogonal to the optical axis of the optical fiber 3 is 10 °. Therefore, the difference in the incident angle of each light beam is extremely small to the extent that it does not have any influence on the beam spot positioning process. Therefore, in the following description, the difference in the incident angle of each light beam is ignored.

  FIGS. 3A to 3C are schematic cross-sectional views on a plane including the optical axis of the optical fiber 3 showing the locus of light incident on the optical fiber portion 10a of the present embodiment. The two lines shown in FIG. 3 indicate the light rays passing through the outermost side from the light from the LD passing through the plane including the optical axis of the optical fiber 3. 3A shows the locus of light when the light from the LD is incident on the core 31 at the first end face 11. FIG. 3B shows the clad 32 at the first end face 11. FIG. 3C shows a light trajectory when the light from the LD enters the adhesive layer c or the capillary 4 having the same refractive index on the first end face 11. Each is shown. In addition, in the optical fiber part 10a shown to FIG. 3 (A)-(C), the thickness of each layer differs from the actual for convenience of explaining the transmission state in each layer of light.

  First, a case where light from the LD enters the core 31 will be described. Since the core 31 and the clad 32 satisfy the above condition (3), the light incident on the core 31 on the first end face 11 is the interface between the core 31 and the clad 32 as shown in FIG. Then, total reflection is repeated and the light is transmitted through the optical fiber 3.

  In the optical fiber portion 10a satisfying the above conditions (1) to (3), the light incident on the clad 32 on the first end face 11 does not stay in the clad 32 as shown in FIG. Compared to the core 31 and the adhesive layer c, which have a higher refractive index. Eventually, total reflection occurs only at the interface between the clad 32 and the adhesive layer c and the interface between the capillary 4 and the outside (air), and the light is transmitted through the two layers of the adhesive layer c and the capillary 4.

  Further, in the optical fiber portion 10a satisfying the above conditions (1) to (3), the light incident on the adhesive layer c on the first end face 11 follows the total reflection condition and the interface between the capillary 4 and the outside (air) and the cladding. Total reflection occurs only at the interface between 32 and the adhesive layer c. Therefore, the light incident on the adhesive layer c is transmitted through the two layers of the adhesive layer c and the capillary 4 as shown in FIG. The same applies to the light incident on the capillary 4 having the same refractive index as that of the adhesive layer c. As described above, the light incident on the optical fiber portion 10a that satisfies the above conditions (1) to (3) is transmitted through the core 31 regardless of the location of the first end face 11 other than the core 31. There is always no transmission within the two layers of the adhesive layer c and the capillary 4.

  FIG. 4 is a graph showing the relationship between the amount of deviation from the center of the core 31 to the beam spot forming position on the first end face 11 and the amount of light incident on the optical fiber portion 10a. The horizontal axis represents the amount of deviation from the center of the core 31, and the vertical axis represents the amount of light. Here, d indicates the diameter of the core 31. A solid line indicates the amount of light transmitted through the core 31, and a broken line indicates the amount of light transmitted through a layer other than the core 31 (see FIGS. 3A to 3C). As shown in FIG. 4, when the beam spot is formed at the center of the core 31 (deviation amount 0), the amount of light transmitted through the adhesive layer c and the capillary 4, that is, the amount of light received by the light receiving unit 5 is substantially zero. Thus, the amount of light transmitted through the core 31 is maximized. As the beam spot formation position deviates from the center of the core 31, the amount of light transmitted through the core 31 decreases instead of the amount of light transmitted through the cladding 32 and the capillary 4 increasing.

  Therefore, the amount of light transmitted through the clad 32 and the capillary 4 is detected, and the formation of the beam spot is controlled by negative feedback control of the formation position of the beam spot so that the amount of light is minimized (0 in the present embodiment). Positioning can be performed to guide the position to the core center.

  Based on the above principle, in the first embodiment, positioning is performed as follows. First, when executing the positioning, the controller 7 causes the condenser lens 2 to vibrate slightly (wobble) with a constant period and a constant amplitude in a direction orthogonal to the optical axis of the lens 2 via the actuator 8. As a result, the position of the beam spot formed on the first end face 11 by the light emitted from the LD continuously changes slightly.

  The light emitted from the condenser lens 2 converges and enters the first end face 11 of the optical fiber portion 10a. Of the light incident on the optical fiber portion 10 a, the light transmitted through the clad 32 and the capillary 4 is received by the light receiving portion 5 disposed on the second end face 12.

  The light receiving unit 5 detects the light amount of the received light and outputs a signal corresponding to the light amount to the controller 7. Based on the signal from the light receiving unit 5, the controller 7 performs negative feedback control so that the beam spot formed by the light from the LD on the first end surface 11 and the center of the core 31 substantially coincide. Specifically, the controller 7 detects the current beam spot formation position on the first end surface based on the change in the detected light amount accompanying the minute change in the beam spot formation position due to wobbling. Then, the controller 7 passes the actuator 8 so that the light amount detected by the light receiving unit 5 becomes 0, in other words, the beam spot formed on the first end face 11 and the center of the core 31 substantially coincide. The condensing lens 2 is driven and controlled in a direction orthogonal to the optical axis of the lens 2. As a result, the position of the beam spot on the first end face 11 is moved. The state where the beam spot and the center of the core 31 coincide with each other is a state where the coupling efficiency is highest, that is, a state where optical communication with high accuracy is performed. As described above, in this embodiment, the controller 7 performs the driving in the direction orthogonal to the optical axis of the lens 2 simultaneously with the wobbling of the condenser lens 2. Therefore, the driving mechanism for positioning in the optical communication apparatus 100 is shared, and a simple configuration is realized.

  The above is the description of the optical communication apparatus according to the first embodiment. Next, a second embodiment will be described. The optical communication device according to the second embodiment includes an optical fiber portion 10b shown in FIG. 5 as an alternative to the optical fiber portion 10a in the optical communication device 100 according to the first embodiment. 5A is a cross-sectional view of the optical fiber portion 10b in a plane including the optical axis of the optical fiber, and FIG. 5B is a cross-sectional view taken along the line AA in FIG. 5A. Since each member other than the optical fiber portion 10b and each member constituting the optical fiber portion 10b are the same as those of the optical communication device 100 of the first embodiment, description thereof will be omitted with reference to FIG.

  As shown in FIG. 5, in the optical fiber portion 10b, the light receiving portion 5 is disposed not in the second end face 12 but in a plane parallel to the optical axis of the optical fiber. As shown in FIG. 5B, in the optical fiber portion 10b, the light receiving portion 5 is partially in contact with the circumferential surface of the capillary 4, more specifically, the circumferential surface on the second end surface 12 side. It is arranged in a state. The light receiving unit 5 is coupled to the capillary 4 via an adhesive 13. The adhesive 13 has a refractive index substantially equal to the refractive index of the capillary 4 so that the light passing through the capillary 4 is accurately guided to the light receiving unit 5.

  Similarly to the first embodiment, in the second embodiment, n1 is set to 1.494, n2 is set to 1.460, n3 is set to 1.464, and nc is set to 1.494. Accordingly, the optical fiber portion 10b of the second embodiment also satisfies the conditions (1) to (3). Therefore, the transmission state of the light incident on the optical fiber portion 10a is as shown in FIGS. 3A to 3C as in the first embodiment.

  The second end surface 12 is designed as a total reflection surface so that light incident on the end surface 12 is guided to the light receiving unit 5. Specifically, as shown in FIG. 5B, the second end face 12 is inclined with respect to the optical axis of the optical fiber 3 so that the apex angle in a plane including the optical axis of the optical fiber is θ1. .

  The vertex angle θ1 in the second embodiment will be verified. FIG. 6 is a schematic cross-sectional view on a plane including the optical axis of the optical fiber related to the optical fiber portion 10b for verifying the apex angle θ1. In general, depending on the light rays included in the light incident on the clad 31 at the first end surface 11, the incident angle θ <b> 2 at the second end surface 12 is the light incident on the adhesive layer c or the capillary 4 at the first end surface 11. There is a case where a value smaller than the incident angle at the second end face 12 with respect to the included light rays and close to the total reflection angle θ3 at the second end face 12 may be taken. Therefore, the apex angle θ1 may be determined so as to ensure a state in which the incident angle θ2 is larger than the total reflection angle θ3 (θ2> θ3).

First, the total reflection angle θR at the interface between the core 31 and the clad 32 required for light to transmit in the core 31 is:
n3sinθR = n2sin90 °
Therefore, it is 85.764 °.

Assuming that convergent light of NA = 0.109 is incident on the optical fiber portion 10b, the angle θ9 formed by the light beam Lc passing through the center of the convergent light and the outermost light beam Lo of the convergent light is
sin θ9 = n3 cos θR
Therefore, it is 6.208 °.

In addition, since the angle θ0 formed by the first end surface 11 and a surface orthogonal to the optical axis of the optical fiber 3 is assumed to be 10 °, the angle θ8 formed by the light beam Lc and the central axis Lax of the optical fiber 3 is
sin θ8 = n3 sin θ0
Therefore, it is 4.727 °.

The incident angle θ7 of the light ray Lo at the first end face 11 is
θ7 = θ0 + θ8−θ9
Therefore, it is 8.159. Further, the refraction angle θ6 at the first end face 11 of the light ray Lo is
sin θ7 = n2sin θ6
Therefore, it is 5.823 degrees.

The incident angle θ5 of the light beam Lo traveling in the clad 32 with respect to the interface between the clad 32 and the adhesive layer c is:
θ5 = 90− (θ0−θ2)
From the above, it is 85.823 °. The refraction angle θ4 of the light beam Lo with respect to the interface between the cladding 32 and the adhesive layer c is
n2sin θ5 = ncsin θ4
Therefore, it is 77.071 °.

Here, the total reflection angle θ3 at the second end face 12 is
n1sin θ3 = sin90 = 1
Therefore, it is 42.016 degrees.

In order for the light beam Lo transmitted through the adhesive layer c and the capillary 4 to be totally reflected by the second end face 12, as described above, the following condition (4)
θ2> θ3 (4)
As long as is satisfied.
Since θ2 = θ4-θ1, the condition (4) is
θ4-θ3> θ1 (5)
It can be rewritten as

Substituting the values of θ4 and θ3 into the condition (5), the apex angle θ1 becomes the following condition (6),
θ1 <35.055 ° (6)
Should be satisfied.

  In addition, the incident angle with respect to the 1st end surface 11 of the light ray contained in the said convergent light differs. However, as described above, the difference is extremely small. Therefore, the verification for the light beam Lo described above is applied to other light beams, that is, the entire convergent light. As a result, in the configuration of the second embodiment, the light incident on each layer 32, c, 4 other than the core 31 is designed by designing the second end face 12 so that the apex angle θ1 is larger than 35.555 °. Are totally reflected by the second end face 12 and guided to the light receiving section 5.

  In order to make light incident on the light receiving section more reliably, it is also beneficial to apply a reflective film to the second end face 12. A reflective film can also be applied to the circumferential surface of the capillary 4 so as not to prevent light from entering the light receiving unit 5.

  The positioning process in the optical communication apparatus 100 according to the second embodiment is the same as that described above except that light incident on the clad 32 or capillary 4 is incident on the light receiving unit 5 after being deflected directly or by the second end face 12. This is performed in the same manner as in the embodiment.

  In the optical communication devices of the first embodiment and the second embodiment described above, the capillary 4 is used as a light transmission means that guides light incident on a region other than the core 31 on the first end face 11 to the light receiving unit. The light transmitting means does not need to be a transmissive member that guides light to the light receiving portion by transmitting light as in the capillary 4. For example, in the optical communication device 100 according to the third embodiment described below, a reflection member is used as the light transmission means.

  FIG. 7 is a diagram illustrating the configuration of the optical communication device 100 according to the third embodiment. In FIG. 7, the same members as those of the optical communication apparatus 100 of the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted. The optical communication device 100 according to the third embodiment includes an optical fiber portion 10c and a light receiving portion 5 'as an alternative to the optical fiber portion 10a in the optical communication device 100 according to the first embodiment.

  The optical fiber portion 10 c includes a core 31, an optical fiber 3 including a clad 32, and a capillary 4. As shown in FIG. 8, in the end face where light from the LD of the optical fiber portion 10 c enters, that is, the first end face 11, a region (here, a mirror surface) M having a high reflectivity is formed in a region other than the core 31. It has been subjected. In addition, the 1st end surface 11 is cut | disconnected by surfaces other than the surface orthogonal to the optical axis of the optical fiber 3 similarly to said each embodiment. The light receiving portion 5 ′ is disposed in the optical path of the light reflected by the first end surface 11. By arranging and configuring the optical fiber portion 10c and the light receiving portion 5 ′ in this way, the light reflected by the first end face 11 returns to the LD side, thereby affecting the APC (Auto Power Control) circuit that adjusts the output of the LD. In addition, the light reflected by the first end face 11 can be guided to the light receiving unit 5 ′ without using a deflecting member.

  FIG. 9 is a diagram schematically illustrating a locus of light incident on the optical fiber portion 10 c in a plane including the optical axis of the optical fiber 3 in the optical communication device 100 according to the third embodiment. FIG. 9A shows the locus of light when light from the LD is incident on the core 31 just at the first end surface 11, and FIG. 9B shows the light from the LD at the core 31 at the first end surface 11. The trajectory of light when entering the other area, that is, the mirror surface M is shown.

  As shown in FIG. 9A, light incident on the core 31 on the first end face 11 is transmitted through the optical fiber 3 while repeating total reflection at the interface between the core 31 and the clad 32. At this time, almost no light is incident on the light receiving portion 5 ′. That is, the amount of light detected by the light receiving unit 5 'is substantially equal to zero. On the other hand, the light incident on the mirror surface M is reflected by the mirror surface M and incident on the light receiving portion 5 'as shown in FIG. 9B. As a result, the relationship shown in FIG. 4 is also obtained in the optical communication apparatus 100 of the third embodiment.

  Accordingly, the light amount of the light reflected by the mirror surface M on the first end face 11 is detected by the light receiving unit 5 ′, and the beam spot formation position is negatively feedback controlled so that the light amount becomes zero, thereby the beam spot. Positioning can be performed so as to guide the formation position to the center of the core. Since the wobbling control and the negative feedback control performed by the controller 7 at the time of positioning are the same as those in the first embodiment, description thereof is omitted here.

  As in the optical communication device 100 of each of the above embodiments, the amount of light incident on a region other than the core 31 on the first end face 11 (incident end face of the optical fiber 3) of the optical fiber portions 10a to 10c becomes zero. Thus, by performing negative feedback control of the beam spot formation position, the signal light emitted from the LD can be guided to the core center with high accuracy. In addition, the optical communication device 100 of each embodiment is configured at a very low cost because highly accurate positioning is performed without using an expensive optical member for extracting light for performing negative feedback control as in the prior art. be able to.

  Since the wobbling frequency is lower than the frequency of the signal light transmission band, it does not affect optical communication using signal light. Therefore, the controller 7 can execute the positioning process even during optical communication. For example, when the optical communication device 100 is used under severe environmental conditions in which vibration is always applied, the above-described positioning may be performed at all times. Further, when the environmental conditions are relatively mild and only the positional deviation due to the change with time needs to be taken into consideration, it may be executed periodically or at an arbitrary timing. If the positioning is not performed, the controller 7 does not move the condenser lens 2 (hold).

  The above is the embodiment of the present invention. In addition, the optical communication apparatus 100 of each embodiment can have the same effect by modifying as follows.

  In each of the above embodiments, the refractive indexes of the cladding 32, the adhesive layer c, and the capillary 4 are set as n2 <nc = n1, but each member is satisfied as long as the above conditions (1) and (2) are satisfied. The refractive indexes of 32, c, and 4 can be arbitrarily set. For example, the refractive index (n1) of the capillary 4, the refractive index (n2) of the cladding 32, and the refractive index (n3) of the core 31 are fixed values. On the other hand, as long as the above condition (2) is satisfied, the adhesive layer c having a refractive index other than the refractive index of the above embodiment can be used. Even when an adhesive having a refractive index other than that in the above embodiment is used, the light incident on other than the core 31 travels through any one of the clad 32, the adhesive layer c, and the capillary 4.

  Particularly in the second embodiment, the NA of the convergent light incident on the optical fiber portion 10b and the angle (θ0) formed by the first end face 11 and the plane perpendicular to the optical axis of the optical fiber 3 are the same as those in the above embodiments. When set, if each refractive index n1, n2, nc satisfies the above conditions (1) and (2), the optical fiber portion 10b is configured so that the apex angle θ1 satisfies the above condition (6). For example, the light incident on the second end face 12 can always be totally reflected.

  Further, when the configuration satisfying the condition (1) is satisfied by setting n1 = n2, there is a possibility that the light beam is transmitted through the cladding 32 in the vicinity of the second end face 12. However, the thickness of the clad 32 is sufficiently smaller than the thickness of the capillary 4. Accordingly, the light beam passing through the clad 32 in the vicinity of the second end face 12 is only a very small amount of the total light flux incident on the optical fiber portions 10a and 10b, and has no influence on the implementation of the present invention. is not. In the case where n1 = n2, it is more preferable that the light amount detecting means is configured in such a shape that it can pass through the clad 32 in the vicinity of the second end face 12 and can also receive the light beam emitted behind the second end face 12.

  In each of the above-described embodiments, the configuration is shown in which the position of the beam spot formed by the light from the LD on the first end surface 11 is directed toward the core 31 by driving and controlling the condenser lens 2. Here, the beam spot moving means may have a configuration other than the configuration in which the condenser lens 2 is driven and controlled. FIG. 10 is a diagram illustrating a schematic configuration of an optical communication device 100 ′ that is a modification of the optical communication device 100 of the first embodiment. The optical communication device 100 ′ has a deflection member K between the condenser lens 2 and the optical fiber portion 10 a. In the optical communication device 100 ′, the controller 7 does not drive the condenser lens 2 but drives the deflection member K via the deflection member actuator 9 to thereby form a beam formed on the first end surface 11. The spot position is moved. The point that the controller 7 wobbles the condenser lens 2 via the actuator 8 is the same as in the first embodiment. That is, in the optical communication apparatus 100 ′, the wobbling means and the beam spot moving means are configured separately and independently. As the deflecting member K, a vertex angle variable prism shown in FIG. 11 is exemplified.

  FIG. 11 is a cross-sectional view showing an example of the variable apex angle prism 20. The variable apex angle prism 20 includes two parallel glass plates 21 and 22 and an elastic bellows cover 23 sealed by the two glass plates 21 and 22. The cover 23 is filled with a liquid such as silicone oil. Each glass plate 21 and 22 is hold | maintained by glass holding | maintenance part 24a-24d. The glass holding part 24a is held by the apex angle adjusting part 27 so as to be movable. Specifically, the glass holding portion 24 a is screwed to a lead screw 26 that is rotatable by the motor portion 25. Therefore, as the lead screw 26 rotates, the glass holding portion 24a moves forward and backward in the α direction (the extending direction of the lead screw 26) in the drawing. As a result, the apex angle θ formed by the glass plates 21 and 22 changes, and the optical path of the light transmitted through the apex angle variable prism 20 can be moved (from the broken line to the solid line in the figure). Therefore, by disposing the two apex angle variable prisms 20 so that the moving direction of the optical path corresponds to two directions orthogonal to the traveling direction of light and orthogonal to each other, without driving the condenser lens 2, The position of the beam spot on the first end face 11 can be moved.

  Other examples of the deflecting member K include the following configurations. For example, the variable vertex angle prism 20 shown in FIG. 11 has been described assuming a so-called uniaxial variable type that can move the optical path only in a predetermined direction. It is also effective to use a type. A set of two wedge-shaped prisms may be used as the deflecting member K. In this case, light can be deflected by changing the position of each wedge by tilting or rotating each wedge prism. It is also possible to move the position of the beam spot on the first end face 11 by driving the LD itself in a direction orthogonal to the straight traveling direction of the light. Further, it is possible to move the position of the beam spot using both the condenser lens 2 and the deflecting member K.

  The modification examples of the means for moving the beam spot forming position on the first end face 11 have been described above, but these can also be used for the optical communication devices of the second embodiment and the third embodiment.

  In the first embodiment and the second embodiment, the transmissive capillary 4 is used as means for transmitting the light incident on the region other than the core 31 on the first end surface 11 to the light receiving unit 5. Thus, by using the capillary which has been used for the purpose of protecting the optical fiber 3 as a light transmission means as it is, positioning of light from the LD with respect to the optical fiber with an inexpensive configuration without increasing the number of components. Is realized. Here, as long as an inexpensive configuration can be maintained, it is not always necessary to use a capillary as the light transmission means. In the third embodiment, the capillary 4 is used as in the other embodiments. Here, when the optical fiber 3 has a sufficient strength against an unintended force applied from the outside, the capillary 4 does not need to be provided.

It is a figure showing schematic structure of the optical communication apparatus of 1st embodiment of this invention. It is a figure which expands and shows the optical fiber part of 1st embodiment. It is a figure which shows typically the locus | trajectory of the light which injects into the optical fiber part of 1st embodiment. It is a graph showing the relationship between the deviation | shift amount from a core center to a beam spot formation position in the 1st end surface, and the light quantity of the light which injected into the optical fiber part. It is a figure which shows the structure of the optical fiber part of 2nd embodiment. It is a cross-sectional schematic diagram in the plane containing the optical axis of the optical fiber regarding the optical fiber part for verifying vertex angle (theta) 1 of 2nd embodiment. It is a figure showing schematic structure of the optical communication apparatus of 3rd embodiment. It is a figure which expands and shows the 1st end surface of the optical fiber part of 3rd embodiment. In the optical communication apparatus of 3rd embodiment, it is a figure which shows typically the locus | trajectory of the light which injects into an optical fiber part in the plane containing the optical axis of an optical fiber. It is a figure which shows schematic structure of the modification of the optical communication apparatus of 1st embodiment. It is sectional drawing which shows an example of a vertex angle variable prism.

Explanation of symbols

2 condensing lens 3 optical fiber 31 incident end face 32 clad 4 capillary 5 5 ′ light receiving part 7 controller 10a, 10b, 10c optical fiber part 11 first end face (incident end face)
100, 100 'optical communication device

Claims (23)

A light source;
An optical fiber configured of a core and a clad, having an incident end face on which light from the light source is incident, and transmitting the light incident on the core at the incident end face;
Detecting means for detecting the amount of the light incident on a region other than the core on the incident end face;
Moving means for moving the position of the beam spot on the incident end face;
An optical communication apparatus comprising: control means for performing negative feedback control on the moving means so that the light quantity becomes a minimum value. An optical communication apparatus according to claim 1 is provided.
An optical communication apparatus, further comprising: a light transmission unit that is integrally formed on a circumferential surface of the optical fiber and that transmits the light incident on a region other than the core on the incident end surface to the detection unit. The optical communication device according to claim 2,
The light transmission means has a first end surface in the same plane as the incident end surface and a second end surface located on the opposite side of the first end surface, and covers the entire circumferential surface. A light cylindrical member,
When the refractive index of the cylindrical member is n1 and the refractive index of the cladding is n2, the refractive index n1 and the refractive index n2 are as follows:
n2 ≦ n1 (1)
An optical communication device characterized by satisfying the above. The optical communication apparatus according to claim 3.
The cylindrical member and the clad are bonded with an adhesive having a refractive index nc, and the refractive index nc is the following condition (2):
n2 ≦ nc ≦ n1 (2)
An optical communication device characterized by satisfying the above. The optical communication device according to claim 3 or 4,
The optical communication apparatus according to claim 1, wherein the detecting means includes a donut-shaped light receiving portion whose light receiving surface is in contact with the entire area of the second end surface. The optical communication device according to any one of claims 3 to 5,
An optical communication apparatus, wherein the cylindrical member is coated with a reflective film on a circumferential surface. The optical communication apparatus according to claim 3.
The second end surface is inclined at a predetermined angle with respect to the optical axis of the optical fiber, and is configured as a reflecting surface that guides light incident on the second end surface to a light receiving portion of the detection means. Optical communication device. The optical communication device according to claim 7.
An optical communication device, wherein a film for increasing the reflectance is deposited on the second end face. In the optical communication device according to claim 7 or 8,
The optical communication device according to claim 1, wherein the light receiving portion of the detecting means is disposed on a surface substantially parallel to the optical axis of the optical fiber. The optical communication device according to any one of claims 7 to 9,
The optical communication device, wherein the light receiving unit is joined to the cylindrical member through a translucent material having a refractive index equal to or higher than that of the cylindrical member. The optical communication device according to any one of claims 3 to 10,
The optical communication device, wherein the cylindrical member has a function of protecting the optical fiber. The optical communication device according to claim 2,
The light transmitting means has a film having a higher reflectance than the core disposed in a region other than the core on the incident end surface,
The optical communication apparatus, wherein the detection unit includes a light receiving unit in an optical path of light reflected by a region other than the core on the incident end surface. The optical communication device according to any one of claims 1 to 12,
The optical communication apparatus, wherein the incident end face is inclined with respect to an optical axis of the optical fiber. The optical communication device according to any one of claims 1 to 13,
The moving means moves a condensing lens for condensing the light emitted from the light source onto the optical fiber in a direction perpendicular to the optical axis of the condensing lens, thereby moving the position of the beam spot. An optical communication device characterized in that the optical communication device is moved. The optical communication device according to any one of claims 1 to 13,
The optical communication apparatus, wherein the moving means moves the position of the beam spot by driving the light source in a direction orthogonal to a direction in which light emitted from the light source goes straight. The optical communication device according to any one of claims 1 to 13,
The moving means has a transmission type deflection member between the light source and the optical fiber, and moves the position of the beam spot by deflecting the light by the transmission type deflection member. Communication device. The optical communication device according to any one of claims 1 to 16,
The optical communication apparatus characterized in that the moving means moves the position of the beam spot in a predetermined direction while being slightly changed periodically. The optical communication device according to claim 17.
The light emitted from the light source is modulated by information,
The optical communication apparatus, wherein the moving means slightly changes the position of the beam spot at a predetermined frequency lower than a frequency of a transmission band of the information by the light. The optical communication device according to claim 17 or 18,
The moving means finely vibrates a condensing lens for condensing the light emitted from the light source onto the optical fiber in a direction perpendicular to the optical axis of the condensing lens, thereby An optical communication apparatus characterized in that the position is slightly changed. The optical communication device according to claim 17 or 18,
The optical communication apparatus characterized in that the moving means minutely changes the position of the beam spot by causing the light source to slightly vibrate in a direction orthogonal to a direction in which light emitted from the light source goes straight. The optical communication device according to claim 17 or 18,
The moving means has a transmission type deflection member between the light source and the optical fiber, and moves the position of the beam spot by deflecting the light by the transmission type deflection member. Communication device. The optical communication device according to claim 16 or claim 21,
The optical communication apparatus, wherein the transmission type deflection member is a variable apex angle prism capable of changing an apex angle. The optical communication apparatus according to any one of claims 1 to 22,
An optical communication apparatus characterized in that the negative feedback control by the control means is performed simultaneously with the transmission of the light modulated by information.

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