JP2009055556A - Optical module and optical pulse testing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize an optical pulse testing device (OTDR) by light-transmitting/receiving a testing light and a return light, and a monitor communication light, by means of a single unit. <P>SOLUTION: An optical module 21 which light-transmits/receives the testing light of short wave, while light-receiving the monitor communication light for the fault detection of an optical fiber 6 inside a PON consists of a semiconductor collimator 31, which emits the testing light, an APD32 which light-receives the return light thereof; a PD33 which light-receives the monitor communication light; an incident portion 34, to which the monitor communication light and the return light are incident, and emits the testing light from the semiconductor collimator 31 to the optical fiber 6; a dichroic mirror 35, which emits the monitor communication light from the incident portion 34 to the PD33, separates and emits the return light to another optical path 44 and emits the testing light, from the semiconductor collimator 31 to incident portion 34; and a half mirror 36 which emits the testing light from the semiconductor collimator 31 to the dichroic mirror 35, and emits the separated return light to the APD32 by the dichroic mirror 35. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a network (PON; Passive Optical Network) that transmits signal light via an optical fiber laid as an optical line from a transmission device on the center station side to an optical terminal via an optical branching unit. , An optical module that transmits and receives test light having a wavelength shorter than that of PON communication light in order to detect an optical fiber failure from the user optical terminal side, and an optical pulse tester (OTDR; Optical Time Domain) using this optical module Reflectometer).

  As a means for detecting from the user optical terminal side an optical fiber failure between the optical branching device and the user optical terminal in the PON described above, there is a failure search system disclosed in Patent Document 1 below.

  FIG. 5 is a functional block diagram showing a configuration of an OTDR used for optical fiber failure detection in Patent Document 1 below. As illustrated, the OTDR 100 includes an operation unit 101, a timing generator 102, a light source 103, an optical coupler 104, a light receiver 105, an amplifier 106, an A / D converter 107, and a processing unit 108. The display unit 109 is substantially configured.

  The operation unit 101 sets the wavelength of light emitted from the light source 103 by a user's operation to a desired value, and receives data related to the repetition period.

  The timing generator 102 sends a timing signal to the light source 103 so that light having a predetermined wavelength and pulse width is generated from the light source 103 at a predetermined repetition period based on the data regarding the setting input from the operation unit 101. Output.

  The light source 103 is composed of, for example, a laser diode (LD), and a light having a wavelength and a pulse width corresponding to the data for setting the input wavelength and pulse width, and a repetition period corresponding to the data for setting the input repetition period. And is emitted as test light to one end of the optical fiber via the optical coupling unit 104.

  At this time, the test light incident on the optical fiber to be measured propagates in the optical fiber of the PON toward the optical splitter. In the propagation process, return light is generated in the optical fiber due to backscattering and Fresnel reflection. The return light propagates in the optical fiber and enters the OTDR 100 from one end of the optical fiber. The optical coupler 104 emits the return light incident in the OTDR 100 to the light receiver 105.

  The light receiver 105 receives the return light returned from the optical fiber, converts the return light into an electrical signal, and outputs the electrical signal to the amplifier 106.

  The amplifier 106 amplifies the electrical signal output from the light receiver 105 and outputs the amplified electrical signal to the A / D converter 107.

  The A / D converter 107 A / D converts the electrical signal output from the amplifier 106 and outputs the A / D converted electrical signal to the processing unit 108.

  The processing unit 108 receives a trigger synchronized with the pulse input from the timing generator 102, performs a process of averaging measurement data included in the electrical signal output from the A / D converter 107, and then performs logarithmic conversion. And a function of calculating the propagation characteristic of the optical fiber with respect to the test light and a function of displaying the calculated propagation characteristic of the optical fiber on the display unit 109.

  Although omitted in FIG. 5, the above-described OTDR 100 incorporates a communication light monitoring light receiver 120 for monitoring normal communication light transmitted through the optical fiber in addition to the test light. . As shown in FIG. 6A, the communication light monitor light receiver 120 is connected to an optical fiber from a connector different from the optical coupling unit 104 described above, and is connected to a signal processing unit dedicated to monitor communication light. Yes. Furthermore, the signal processing unit is connected to the display unit 109 described above, and can display the propagation characteristic of the monitor communication light on the display unit 109 shown in FIG.

  Further, as shown in FIG. 6B, a changeover switch 130 is further provided in the OTDR 100, and an optical coupler 104 and a communication light monitor light receiver 120 are connected to the changeover switch (optical switch) 130 for use. The optical coupler 104 and the communication light monitor light receiver 120 can be switched accordingly.

Further, as shown in FIG. 6C, a configuration in which an optical coupler 140 is provided in the OTDR 100 and the optical coupler 104 and the communication optical monitor light receiver 120 are connected to the optical coupler 140 is also conceivable.
WO2005 / 003714 Publication

  However, in the configuration shown in FIG. 6A, in addition to the communication light monitor light receiver 120 being incorporated in the OTDR 100, an optical fiber is connected to each of the optical coupler 104 and the communication light monitor light receiver 120. Therefore, there is a problem that the configuration of the OTDR 100 is complicated and the OTDR 100 (housing 101) is increased in size.

  Further, in the configuration as shown in FIG. 6B, there is one connector for connecting the optical fiber, but since the optical switch 130 is mounted, the inside of the OTDR 100 is still a complicated configuration. Since the optical switch 130 is expensive, there is a problem that the cost is increased.

  Further, the configuration as shown in FIG. 6C has a problem that the configuration is complicated as in FIG. 6B because the optical coupler 140 is mounted instead of the optical switch 130. In general, since an optical coupler is less expensive than an optical switch, the configuration of FIG. 6C using an optical coupler has an advantage that the cost is lower than the configuration of FIG. 6B using an optical switch. However, there is also a problem that the loss of light receiving sensitivity due to the branching loss of the optical coupler is large (for example, the optical coupler having a branching ratio of 50%: 50% decreases about 3 dB).

  Therefore, in order to solve the above problems, the present invention reduces the size by incorporating an optical module capable of transmitting and receiving test light, its return light, and monitor communication light alone, and this optical module. An object of the present invention is to provide an optical pulse tester (OTDR) that can be realized.

Next, means for solving the above problems will be described with reference to the drawings corresponding to the embodiments.
The optical module according to claim 1 of the present invention receives PON communication light and tests light set to a wavelength shorter than the PON communication light in order to detect a failure of the optical line 6 in the PON. An optical module 21 that transmits and receives light as light,
A semiconductor collimator 31 for emitting the test light;
A short wavelength receiver 32 for receiving the return light of the test light;
A long wavelength light receiver 33 for receiving the communication light of the PON;
The incident portion 34 that emits the test light emitted from the semiconductor collimator 31 to the optical line 6 in the PON, while the communication light and the return light of the PON are incident thereon,
The semiconductor collimator that emits the communication light of the PON from the incident portion 34 to the long-wavelength light receiver 33, separates the return light into another optical path 44, and enters from the other optical path 44. A first beam splitter 35 for emitting the test light emitted from 31 to the incident portion 34;
The test light emitted from the semiconductor collimator 31 is emitted to the first beam splitter 35, and the return light separated by the first beam splitter 35 is emitted to the short wavelength receiver 32. Beam splitter 36 of
It is characterized by comprising.

  The optical module according to claim 2 is characterized in that the first beam splitter 35 is formed of a dichroic mirror and the second beam splitter 36 is formed of a half mirror.

  The optical module according to claim 3 is characterized in that the test light and the return light are 0.65 μm wavelength light.

  The optical module according to claim 4 is characterized in that the test light and the return light are 0.78 μm wavelength light.

  An optical pulse tester according to a fifth aspect includes the optical module 21 according to any one of the first to fourth aspects.

  According to the optical module of the first aspect of the present invention, the first beam splitter receives the test light (short wavelength light) emitted from the semiconductor collimator with respect to the upward light from the user optical terminal toward the center station. For light in the downstream direction, emitted from the center station toward the user optical terminal, the long and short wavelength light is separated and the PON communication light (long wavelength light) is emitted to the long wavelength receiver. At the same time, the return light (short wavelength light) of the test light is emitted toward the second beam splitter via another optical path. The second beam splitter emits the test light emitted from the semiconductor collimator toward the first beam splitter for the upstream light, and the first beam splitter for the downstream light. The return light separated by is emitted toward the short wavelength receiver. As a result, the PON communication light that is long wavelength light, the test light that is short wavelength light, and the return light can be transmitted and received alone.

  Further, since the first beam splitter is composed of a dichroic mirror, light of a specific wavelength can be reflected in an arbitrary direction, and only the test light or its return light can be easily separated into another optical path. Further, since the second beam splitter is composed of a half mirror, a part of the test light (upward light) emitted from the semiconductor collimator is transmitted and a part of the return light (downward light) is transmitted. Reflected by the half mirror, the optical path changes and enters the short wavelength receiver.

  Furthermore, the test light and its return light are 0.65 μm or 0.78 μm wavelength light, indicating that general PON communication light (for example, 1.31 μm wavelength light in the upstream direction and 1.55 μm wavelength light in the downstream direction). ) By using an optical filter installed in the optical line on the user's home side in order to remove the 1.65 μm wavelength light transmitted from the center station side for the transmission test because it has a shorter wavelength and does not affect the communication light. Is not cut, so it is suitable as test light.

  Further, the optical pulse tester (OTDR) can be reduced in size by including an optical module capable of transmitting and receiving long and short wavelength light alone.

Embodiments of the present invention will be specifically described below with reference to the drawings.
FIG. 1 is an explanatory diagram showing an example of a PON type FTTH (; Fiber to the Home).

  As shown in FIG. 1, the FTTH 1 is composed of a center station 2, a first optical branching unit 3, a second optical branching unit 4, and a user optical terminal 5 on the communication carrier side. Are connected to each other by an optical fiber 6. In FIG. 1, user optical terminals other than the user optical terminals 5Ea to 5Ed connected to the fifth second optical branching device 4E are omitted for the sake of simplicity.

  In this FTTH1, for example, the communication light in the upstream direction is 1.31 μm wavelength light, and the communication light in the downstream direction is 1.55 μm wavelength light. The upstream direction is the direction from each user optical terminal 5 toward the center station 2, and the downstream direction is the direction from the center station 2 toward each user optical terminal 5.

  The center station 2 emits downstream communication light having a wavelength of 1.55 μm to the first optical splitter 3 and receives upstream communication light having a wavelength of 1.31 μm emitted from the first optical splitter 3.

  The first optical branching unit 3 receives 1.55 μm wavelength downstream communication light from the center station 2, branches the communication light, and outputs the branched communication light to the second optical branching units 4 </ b> A to 4 </ b> H. The first optical branching unit 3 receives the upstream communication light having a wavelength of 1.31 μm emitted from each of the second optical branching units 4 </ b> A to 4 </ b> H, and emits the communication light to the center station 2.

  The second optical branching device 4 (4E) is provided in the vicinity of each user's house (for example, a utility pole), and branches the downstream communication light having a wavelength of 1.55 μm emitted from the first optical branching device 3. Then, the light is emitted to each user optical terminal 5 (5Ea to 5Ed). The second optical branching device 4 (4E) receives the upstream communication light having a wavelength of 1.31 μm emitted from each user optical terminal 5 (5Ea to 5Ed), and also transmits the communication light to the first optical branch. The light is emitted to the container 3.

  In the case of FTTH1 shown in FIG. 1, a total of 32 user optical terminals 5 are installed in each user's home, and 1.55 μm wavelength downlink communication emitted from each of the second optical branching devices 4A to 4H. In addition to receiving light, the received communication light is photoelectrically converted, and a digital signal obtained thereby is output to a computer (PC) of each user (not shown).

Next, the user optical terminal installed in each user's house will be described.
FIG. 2 is an explanatory diagram showing an example of a user optical terminal. Each of the 32 user optical terminals 5 in total includes an optical fiber 6 connected to each of the second optical branching devices 4A to 4H. Is inserted through.

  As shown in FIG. 2, the user optical terminal 5 includes a substantially rectangular parallelepiped housing 10, an optical fiber 6 having a base end connected to the second optical splitter 4 shown in FIG. 1, a mechanical splice 11, The connector 12 is connected to the end of the optical fiber 6, the optical transmitter / receiver 13, and the interface circuit 14.

  The housing 10 accommodates the optical transmission / reception unit 13 and the interface circuit 14 therein, and the optical fiber 6 is wound around and accommodated therein.

  As described above, the base end portion of the optical fiber 6 is connected to the second optical branching device 4, and the terminal end portion is accommodated in the housing 10.

  The mechanical splice 11 is a member that mechanically sandwiches and joins the end portions of the two optical fibers 6 a and 6 b in the housing 10.

  The connector 12 is connected to the terminal portion of the optical fiber 6 in the user optical terminal 5 and is also connected to the optical transmission / reception unit 13. The connector 12 incorporates a filter (not shown) for removing 1.65 μm wavelength light used in the transmission test of the optical fiber 6 performed from the center station 2 side shown in FIG.

  The optical transmitter / receiver 13 converts the optical signal from the optical fiber 6 into a digital signal and outputs the digital signal to the interface circuit 14. The optical transmitter / receiver 13 converts the data signal output from the PC via the interface circuit 14 into an optical signal and outputs the optical signal to the connector 12.

  The interface circuit 14 outputs the digital signal output from the optical transmission / reception unit 13 to a user-side PC connected via a LAN (not shown). Further, the interface circuit 14 outputs the data signal output from the PC to the optical transmission / reception unit 13.

Next, an optical module and an optical pulse tester (OTDR) incorporating this optical module will be described.
FIG. 3 is a functional block diagram showing an embodiment of an optical module and an OTDR according to the present invention, and FIG. 4 is a front sectional view showing an embodiment of the optical module.

  The OTDR 20 in FIG. 3 is a device for detecting a failure of the optical fiber 6 between the second optical branching device 4 and the user optical terminal 5 in the PON described above from the user optical terminal 5 side. In addition, about the OTDR20 demonstrated below, the same code | symbol is attached | subjected to the location which has a function equivalent to the conventional OTDR100 shown in FIG. 5, and the description is abbreviate | omitted.

  As shown in FIG. 3, the OTDR 20 includes an operation unit 101, a timing generator 102, an optical coupler 104, a light receiver 105, an amplifier 106, an A / D converter 107, a processing unit 108, and a display. The unit 109, the optical module 21, and the signal processing unit 37 are included.

  The test light of OTDR 20 is set to a wavelength shorter than that of PON communication light (1.31 μm, 1.55 μm), and particularly preferred is 0.65 μm or 0.78 μm wavelength light.

  As shown in FIG. 3, the optical module 21 includes a semiconductor collimator 31, a short wavelength receiver 32, a long wavelength receiver 33, an incident portion 34, a first beam splitter 35, and a second beam splitter 36. It consists of and.

  The semiconductor collimator 31 converts the above-described test light into parallel light and emits it to the second beam splitter.

  An avalanche photodiode (APD) as the short wavelength light receiver 32 receives the return light of the test light, converts the return light into an electrical signal, and outputs the electrical signal to the amplifier 106.

  A photodiode (PD) as the long wavelength light receiver 33 receives PON communication light as monitor communication light and converts the communication light into an electrical signal.

  The incident unit 34 receives monitor communication light and return light from the optical fiber 6 and emits test light to the optical fiber 6.

  The first beam splitter 35 is composed of a dichroic mirror, and emits monitor communication light incident from the incident portion 34 to the PD 33, and similarly separates return light incident from the incident portion 34 into another optical path for emission. In addition, test light incident from another optical path is emitted to the incident portion 34.

  The second beam splitter 36 is formed of a half mirror, and emits the test light emitted from the semiconductor collimator 31 to the dichroic mirror 35 via another optical path, and emits the return light separated by the dichroic mirror 35 to the APD 32. .

  The signal processing unit 37 amplifies and A / D-converts the electric signal from the PD 33, calculates propagation characteristics, and displays the result on the display unit 109.

Next, the structure of the optical module will be specifically described with reference to FIG.
As shown in FIG. 4, the optical module 21 has a horizontally long and substantially rectangular block-shaped main body 41. An optical path 42 of monitor communication light (long wavelength light) is provided at the left end of the main body 41 in the drawing from the upper surface to the lower surface of the main body 41. In the openings on the upper and lower surfaces of the optical path 42, an incident portion 34 and a long wavelength light receiver 33 (PD) are provided coaxially.

  Further, an optical path 43 of return light (short wavelength light) is provided in parallel with the optical path 42 at the right end of the main body 41 in the drawing. A short wavelength light receiving portion 32 (APD) is provided in an opening portion on the lower surface of the main body 41 of the optical path 43.

  Further, the main body 41 is provided with another optical path 44 orthogonal to the two optical paths 42 and 43 so as to connect the two optical paths 42 and 43 within the main body 41, and the opening is provided with a semiconductor. A collimator 31 is provided.

  A first beam splitter 35 (dichroic mirror) is provided at a connection position between the optical path 42 and the other optical path 44 with a predetermined inclination. Further, a second beam splitter 36 (half mirror) is similarly provided at a connection position between the optical path 43 and the other optical path 44 with a predetermined inclination.

  As shown in FIG. 4, in the optical module 21, the test light emitted from the semiconductor collimator 31 passes through the half mirror 36, travels straight through the other optical path 44, and is reflected at a substantially right angle by the dichroic mirror 35. , And is emitted from the incident portion 34 to the optical fiber 6.

  The return light from the optical fiber 6 is incident on the incident portion 34, is then emitted to the dichroic mirror 35, is reflected by the dichroic mirror 35 at a substantially right angle, is incident on the half mirror 36, and the return light is reflected by the half mirror 36. A part of the light is reflected at a substantially right angle and enters the APD 32.

  Further, the monitor communication light from the optical fiber 6 is incident on the incident portion 34, then is emitted from the incident portion 34 to the dichroic mirror 35, passes through the dichroic mirror 35, and enters the PD 33.

  According to the above-described embodiment, the dichroic mirror 35 emits the test light emitted from the semiconductor collimator 31 to the optical fiber 6, emits monitor communication light from the optical fiber to the PD 33, and also from the optical fiber. Return light is emitted to the half mirror 36 via another optical path 44. The half mirror 36 emits the test light emitted from the semiconductor collimator 31 to the dichroic mirror 35, and emits the return light separated by the dichroic mirror 35 to the APD 32. As a result, the optical module 21 can transmit and receive the monitor communication light, the test light, and the return light alone.

  The dichroic mirror 35 can reflect light of a specific wavelength in an arbitrary direction, so that only return light can be easily separated from light in the upward direction. Further, a part of the test light emitted from the semiconductor collimator 31 is transmitted by the half mirror 36, and a part of the return light is reflected substantially at right angles, so that only the return light enters the APD 32.

  Furthermore, since the test light and its return light are 0.65 μm or 0.78 μm wavelength light, the communication light is not affected, and the 1.65 μm wavelength light transmitted from the center station side for transmission test is removed. In addition, since it is not cut by an optical filter installed on the optical path on the user's home side, it is suitable as test light.

  In addition, the OTDR 20 includes the optical module 21 capable of transmitting and receiving long and short wavelength light alone, thereby enabling a reduction in size.

It is explanatory drawing which shows an example of FT type FTTH. It is explanatory drawing which shows an example of a user optical terminal. It is a functional block diagram which shows the optical module and optical pulse tester by this invention. It is a front sectional view showing an optical module according to the present invention. It is a functional block diagram which shows the conventional optical pulse tester. (A)-(c) It is a functional block diagram which shows a part of conventional optical pulse tester.

Explanation of symbols

6 ... Optical line (optical fiber)
20 ... Optical pulse tester (OTDR)
21 ... Optical module 31 ... Semiconductor collimator 32 ... Short wavelength light receiver (APD)
33 ... Long wavelength receiver (PD)
34 ... Incident part 35 ... First beam splitter (dichroic mirror)
36 ... Second beam splitter (half mirror)
44. Other light paths

Claims (5)

An optical module (21) that receives PON communication light and transmits and receives light set to a wavelength shorter than the PON communication light as test light in order to detect a failure of the optical line (6) in the PON. Because
A semiconductor collimator (31) for emitting the test light;
A short wavelength receiver (32) for receiving the return light of the test light;
A long wavelength receiver (33) for receiving the communication light of the PON;
The incident portion (34) for emitting the test light emitted from the semiconductor collimator to the optical line in the PON, while the communication light and the return light of the PON are incident.
From the semiconductor collimator that emits the communication light of the PON from the incident portion to the long-wavelength light receiver, emits the return light separately into another optical path (44), and enters from the other optical path A first beam splitter (35) for emitting the emitted test light to the incident portion;
A second beam splitter that emits the test light emitted from the semiconductor collimator to the first beam splitter and emits the return light separated by the first beam splitter to the short wavelength receiver; 36)
An optical module comprising:   The optical module according to claim 1, wherein the first beam splitter (35) comprises a dichroic mirror, and the second beam splitter (36) comprises a half mirror.   The optical module according to claim 1, wherein the test light and the return light are 0.65 μm wavelength light.   The optical module according to claim 1, wherein the test light and the return light are 0.78 μm wavelength light.   An optical pulse tester comprising the optical module (21) according to any one of claims 1 to 4.

Images