JP3470867B2 - Optical transceiver module - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical transmitter / receiver module used in an optical communication system in which one (one core) optical fiber is used for both transmission and reception to perform bidirectional communication.

[0002]

2. Description of the Related Art Optical communication devices have been developed with the increase in capacity and long distance of trunk line systems. Currently, research and development of various transmission methods and optical devices compatible with them are in progress for the popularization of optical subscriber systems. However, in order to promote the optical communication of subscriber systems, the price of optical devices is low. Has become a major issue.

In this regard, as shown in FIG. 20, a station side device (OSU: Optical Subscriber) is used.
Unit) and a plurality of subscriber units (ONU: Opti)
The optical network is connected to the cal network unit (SC) using an optical star coupler (SC) 1
Low-priced by adopting the form of communication to a large number of people, achieving high reliability by using SC which is a passive device for optical signal branching, and also using one optical fiber for both transmission and reception (bidirectional) That is, PDS (Passive Double Sta) that enables the construction of an economical system.
r) The system has been proposed by NTT.

This PDS system is described in the document "HP
Design Symposium '95p13-
1-13-22 ".

Here, in the above PDS system, a TCM (Time) for performing bidirectional communication with one optical fiber.
The Compression Multiple) is adopted. In OSU, signals to each ONU are sent to TDM.
(Time Division Multiple), and further converted into a TCM burst optical signal. The converted TCM burst optical signal is transmitted from the OSU as a downlink signal and is branched by the SC to each ONU. vice versa,
The signals transmitted from each ONU to the OSU are allocated to different times from each other by TCM-TDMA (Time Divis).
Ion Multiple Multiple Access) optical signal is converted to an O signal through the SC and the optical fiber as an upstream signal.
Sent to SU.

As a conventional example of such an optical transceiver module, there is one disclosed in Japanese Patent Laid-Open No. 7-104154 (hereinafter referred to as a first conventional example). This first
In the conventional optical transceiver module, a holographic diffraction grating is used as an optical branching element to reduce the size and cost of the optical transceiver module.

The configuration and operation thereof will be described below with reference to FIG. The transmission signal light emitted from the light emitting element 102 mounted on the submount 101 supported by the stem 100 passes through the cover glass 104 attached to the package 103, and is subsequently formed on the emission surface side of the cover glass 104. After being halved by the holographic diffraction grating 105 into 0th-order light and + 1st-order light,
The light is condensed by 6, and only the 0th-order light is incident on the end face of the optical fiber 107.

On the other hand, the received signal light emitted from the optical fiber 107 is condensed by the condenser lens 106 and then incident on the holographic diffraction grating 105, and the 0th order light and +1 are added.
The light is divided into the next light and then transmitted through the cover glass 104, and only the + 1st light enters the light receiving element 108. In addition,
Reference numeral 109 is a light receiving element for a signal light monitor.

By the way, in the PDS system, an SMF (single mode optical fiber) is used similarly to the trunk line system, but its core diameter is as small as 9.5 μm, so that it has a submicron level accuracy in a mounting device for optical fibers and lenses. Required.

As a result, in the configuration of the first conventional example, the adjustment time becomes long and mass production is difficult, which hinders the cost reduction of the optical transceiver module. Further, since the optical components are fixed after the optimum adjustment, there is a problem that the components are misaligned due to temperature and aging, and the performance is deteriorated.

In order to solve the problem of the first conventional example, it is possible to divert the technology of the optical disk device to
It is disclosed in Japanese Patent Publication No. 2509000 (hereinafter, referred to as a second conventional example).

22 to 24 show this second conventional example.
The optical fiber 200 has a core 4 and a clad 205 on its end face.
Has a coating 202 that gives a reflectance difference to the transmission light reflected from the coating 202 by the multi-division light receiving element 225,
The lens servo mechanism 226 is operated by the detection signal. The transmitted light is transmitted through the optical fiber 2 by the servo mechanism 226.
Since it is constantly adjusted to the optimum position of 00, performance deterioration due to temperature and aging does not occur.

[0013]

However, the second conventional example has the following problems.

(1) Since it is a module dedicated to transmission and not a transmission / reception module, it cannot be used in a PDS system.

(2) Since the coating 202 is provided on the surface of the core 204, the transmittance of signal light is deteriorated. However, core 2
If the coating 202 is not provided on the surface of 04, the amount of reflected light is reduced, so that the detection accuracy decreases and the servo accuracy deteriorates.

(3) Coating 2 provided on the clad 205
Since the reflectance of No. 02 changes discontinuously, information on the distance and direction from the core center of the focus position of the transmission light cannot be obtained, and the servo settling time (time until the adjustment is completed) becomes long. As a result, for example, it is not possible to follow the position change of the optical component due to the rapid temperature change.

The problem (3) will be described in detail below with reference to FIG. FIG. 25 shows the uniaxial reflectance distribution of the cross section of the optical fiber and its end face. Now, if the focused beam of transmitted light hits point 1, which is one point on the end face of the optical fiber, since the reflectance is the same on the left and right sides, the servo circuit should move the focused beam to the left or to the right. I can't decide if it should be moved.

In such a case, if the focused beam is moved to the left side, the point 2 (that is, the optical fiber 20
Only when it comes to the left end (in the radial direction of 0), the servo circuit knows that the moving direction is wrong. And then
Move the focused beam to the right. Then, it hits the end point 3 of the core 204. Since the reflectance at this position is different on the left and right sides, the servo circuit can recognize that the focused beam is at the end of the core 204.

However, the center of the core 204 is still unknown. Therefore, the focused beam is still moved to the right. Then, the position of the end (point 4) of the core 204 is known.
Since the center of the core 204 is in the middle of the points 3 and 4, if the moving speed and the moving time are obtained in the previous process, the focused beam can be moved to the center of the core 204.
It is sufficient to move the focused beam from the point 4 to the left by (moving speed from the point 3 to the point 4) × (time taken to move from the point 3 to the point 4) / 2.

However, with this control method, there is much waste in the movement of the focused beam, and the servo settling time becomes long.
In addition, since the center of the core, which is the target of control, can only be known indirectly, an error occurs and the accuracy of servo deteriorates.

Further, due to the problem of (3) above,
The following problems (4) and (5) occur.

(4) Since the transmission data input to the light emitting element before the servo settling does not enter the optical fiber 200, a spillage occurs at the beginning of the transmission data. Further, if a signal is transmitted even after servo settling, the transmission signal overlaps with the light reception signal of the multi-divided light receiving element 225.
The servo operation becomes unstable, and the transmission signal becomes the optical fiber 20.
It will not enter 0.

(5) Power consumption is large because the servo mechanism 226 is operated 24 hours a day. Since the PDS system also serves as a telephone line, it has a battery so that it can be used even during a power outage, but the large power consumption causes an increase in battery capacity, resulting in an increase in price and size.

In addition, there are the following problems.

(6) When the multi-divided light receiving element 225 tries to receive the received light, the received light cannot be obtained because the reflected light for obtaining the servo signal overlaps the received signal.

(7) It does not support wavelength-multiplexed communication of 1.3 μm for transmitted light and 1.5 μm for received light, which is called an ATM-PDS system.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical transceiver module capable of solving the above-mentioned problems of the prior art.

[0028]

SUMMARY OF THE INVENTION An optical transceiver module of the present invention is an optical transceiver module that performs bidirectional communication by using one optical fiber for both transmission and reception, and a light emitting element that emits transmission light and the transmission light. Between the first light branching element that divides the reflected light at the end face of the optical fiber into which the light is guided, the multi-segment light receiving element that receives the reflected light from the end face of the optical fiber, and the light emitting element and the optical fiber Second optical branching element for dividing the transmitted / received light into two, a light receiving element for receiving the received light, and a lens for condensing the transmitted / received light, and the lens or the optical fiber at least in a biaxial direction orthogonal to the optical axis. And an actuator for performing a servo operation to move the optical fiber to the optical fiber.
The tip of the bar is processed into a curved surface consisting of a concave surface or a convex surface.
The amount of transmitted light reflected by the end face of the optical fiber is
The multi-divided light receiving element detects that it changes depending on the light position
Then, based on the detection signal of the multi-divided light receiving element, the actuation
The data is adapted to perform a servo operation, thereby achieving the above object.

Preferably, the actuator has the lens or the optical fiber as an optical axis and 2 orthogonal to the optical axis.
The actuator is configured to perform a three-axis servo operation of moving in the axial direction.

[0030]

Preferably, the actuator is caused to perform a servo operation based on the input transmission data, the transmission data input to the light emitting element is delayed by a servo settling time or more, and position control is performed after the servo settling. The operation of the actuator is stopped while maintaining the position of the target lens or the optical fiber.

Further, preferably, in the actuator,
As the received light during the servo operation stop is incident on the light receiving element, placing the second optical branching device, and a structure to maintain the actuator in the servo operation is stopped upon reception.

Preferably, the multi-divided light receiving element also serves as the light receiving element.

Further, it is preferable that the first light branching element and the second light branching element are formed by one hologram optical element.

Preferably, the second optical branching element is a wavelength branching element.

The operation of the present invention will be described below.

Since the optical transmission / reception module of the present invention comprises the optical branching element for dividing the transmission light and the reception light into two and the light receiving element for detecting the reception light, the bidirectional using one optical fiber is used. Communication becomes possible. Therefore, it can be applied to the PDS system.

Further, according to the construction in which the tip of the optical fiber, that is, the end surface thereof is processed into a curved surface composed of a concave surface or a convex surface
The angle of incidence on the optical fiber changes depending on the position where the transmitted light is focused. Therefore, the reflectance apparently continuously changes depending on the condensing position, and the direction and the moving distance can be known. As a result, the servo settling time can be shortened.
Moreover, since the transmittance does not deteriorate even if the surface of the core of the optical fiber is processed, the light utilization efficiency is high. In addition, since the center of the optical fiber is the apex of the core, the amount of reflected light can be directly known, so that the servo accuracy can be improved.

Further, the actuator is caused to perform a servo operation based on the input transmission data, and the transmission data input to the light emitting element is delayed by the servo settling time or more.
And after the servo settling, according to the configuration in which the operation of the actuator is stopped while maintaining the position of the lens or the optical fiber to be position controlled, the servo mechanism has completed the servo settling when the data is input to the light emitting element. No spill of transmitted data occurs. In addition, even if the transmission signal is incident on the multi-segment light receiving element, the actuator maintains the set position, so that the servo operation becomes unstable even if the transmission signal overlaps the light reception signal of the multi-segment light receiving element during signal transmission. It never happens. Furthermore, since the actuator is temporarily stopped and the current flowing through the servo circuit can be reduced, power consumption can be saved.

More specifically, when transmitting light, it is necessary to make the transmitted light incident on a narrow region of the optical fiber having a core diameter of φ9.5 μm, so that highly accurate positioning (that is, servo operation) is required. When receiving, the received light may be incident on a wide area of the light receiving area φ75 μm of the light receiving element, and high-precision positioning (servo operation) is not required, so that the operation of the servo mechanism can be stopped during reception. , Power consumption can be saved. In this regard, the present inventors have found out.

When the operation of the servo mechanism is stopped, the reflected light from the end face of the optical fiber does not enter the multi-divided light receiving element, so that the received signal can be received correctly.

Further, if the multi-divided light receiving element also serves as a light receiving element, an inexpensive optical transceiver module can be realized.

An inexpensive optical transmission / reception module can also be realized by a configuration in which the first optical branching element and the second optical branching element are formed by one hologram optical element.

Further, according to the structure using the wavelength branching element as the second optical branching element, for example, 1.3 μm light and 1.5 μm light are used.
Since m lights can be separated, wavelength division multiplexing becomes possible.

[0045]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be specifically described below with reference to the drawings.

(Embodiment 1) FIGS. 1 to 13 show Embodiment 1 of the optical transceiver module of the present invention. First, the schematic configuration and operation thereof will be described with reference to FIG.

This optical transmitter / receiver module comprises a semiconductor laser device (L) which is hermetically sealed in a can package.
D) 1, a lens 2, a light branching element (BS) 3, a lens 4, a cylindrical lens (cylindrical lens) 5, and a multi-divided light receiving element (PD) 6 hermetically sealed in a can package. A light branching element (BS) 7, a lens 8 and
Light receiving element (P
D) 9, a lens 10, an actuator (three-axis lens actuator) 11 for finely adjusting the lens 10 in a total of three axial directions of the optical axis and two axial directions orthogonal to the optical axis, a receptacle 12, and these optical components. Optical base to hold 1
3 and 3.

As shown in FIG. 2A, PD 6 has a
It is configured by a circular 8-segment light receiving element in which eight segment cells of h are arranged at equal intervals in the circumferential direction. Alternatively, the square 8-divided light receiving element shown in FIG.

Next, the operation of this optical transceiver module will be described. The laser beam emitted from the LD1, that is, the transmitted light is collimated by the lens 2 and enters the BS3. In BS3, a reflection film is formed on the bonding surface so that 10% of the incident light is reflected.

As a result, 90% of the incident light beam goes straight on and enters the BS 7. In BS7, the incident light is 50
The reflective film is formed so that% of the light is reflected. As a result, 50% of the incident light flux goes straight and enters the lens 10. The incident light flux is condensed by the lens 10 and is incident on the optical fiber 15 fixed to the receptacle 12.

Fresnel reflection causes a maximum of 4% of the light to be reflected at the end face of the optical fiber 15, and this reflected light enters the BS 3 through the optical path opposite to the above, and is reflected here.
The reflected light enters the PD 6 through the lens 4 and the cylindrical lens 5 arranged below the BS 3. PD6
A servo signal in the X-axis direction, the Y-axis direction, and the Z-axis direction (optical axis direction) is obtained by performing a later-described calculation of the photocurrent of each divided cell generated from the reflected light that has entered the.

Based on this servo signal, the actuator circuit 1 (see FIG. 12) causes the servo circuit 43 (see FIG. 12) to align the focus position of the lens 10 with the center of the core of the optical fiber 15.
Fine-tune 1.

On the other hand, the received light emitted from the optical fiber 15 is collimated by the lens 10 and then BS
It is reflected by 7, passes through the lens 8, enters as a convergent light into the PD 9 composed of a two-divided light receiving element, and is converted into a reception signal.

Next, the details of the optical component will be described. FIG. 3 shows the structure of the receptacle 12. The details of this structure are described in the adapter of JLS C5973 "FC04 type single-core optical fiber connector". As a function, it holds the end face of the optical fiber 15 fixed inside the ferrule 14 in the plug (described in detail as the plug of JLS C5973 “FC04 type single-core optical fiber connector”) at a specific position. It is a thing.

The structure having the receptacle 12 as the optical transmission / reception module is called a receptacle type, and is called a first type.
A configuration in which the optical fiber 15 directly goes out of the module as in the conventional example is called a pigtail type. In the first embodiment, the receptacle type is shown, but it goes without saying that the present invention can also be applied to the pigtail type.

As shown in FIG. 4A, the optical fiber 15
The tip of is processed into a convex surface 15a in order to obtain reflected light according to the position of the condensed beam of the lens 10. The concave surface 15b may be processed as shown in FIG.

In the receptacle type, the tip of the optical fiber 15 as the tip of the plug is covered with the ferrule 14 which is a pipe made of ceramics such as zirconia. Processing of the tip of the optical fiber 15, that is, convex surface 15a or concave surface 15b
The processing may be performed by polishing with the optical fiber 15 incorporated in the ferrule 14.

Conventionally, a method has been used in which the ends of the plugs are processed into a convex surface in order to bring the plugs into contact with each other and to optically connect the optical fibers to each other, and the convex surfaces are deformed by mutual contact to reduce optical loss. If the curved surface is used together, the productivity of processing will be further improved.

FIG. 5 shows the structure of the actuator 11.
The lens 10 is fixed to a spiral spring 17 via a lens barrel 16 and is movable in the XYZ axis directions. Lens barrel 16
Three sets of magnetic coils 18 are attached around the axis of the lens 10, and a force proportional to the current flowing therethrough is applied to the lens 10.
This allows the lens 10 to be finely moved in each axial direction. A viscoelastic resin adhesive (not shown) is applied to the spiral spring 17 and functions as a damper.
Reference numeral 19 in the drawing indicates a pole plate, 20 indicates a magnet, and 21 indicates a yoke plate.

In this embodiment, the actuator 11
As the above, an electromagnetic lens actuator is used, but it is also possible to use other actuators such as a piezo actuator and an electrostatic actuator.

In the present embodiment, the lens 10 is finely adjusted in the three-axis directions so that the focal point thereof is aligned with the center of the core of the optical fiber 15, but the optical fiber 15 side may be moved for alignment. It is possible. FIG. 6 shows the structure of such an actuator, a fiber biaxial actuator 30. A metal film is deposited on the optical fiber 15,
When a high electric field is applied to the fiber drive electrode 31, the optical fiber 15 can be finely moved in the XY biaxial directions by electrostatic force. Reference numeral 32 in the drawing denotes a V groove for fixing the optical fiber, and 33 denotes insulating SiO ₂ .

When a glass lens is used as the lens or when a lensless (direct coupling) optical system is used, the Z-axis actuator is unnecessary as described later.
In the case of not using a ferrule like the pigtail type, as shown in FIG.
Processing to 5a can be performed by applying heat to the tip and processing the surface into a spherical surface.

Next, the lenses 2, 4, 5, 8 and 10 will be described. The lens 2 is an aspherical lens made of resin,
The other lenses 4, 5, 8 and 10 are spherical lenses made of resin. Here, the reason why the lens 2 is an aspherical lens is as follows.

In order to make the transmitted light incident on the core of the optical fiber 15, it is necessary to narrow the light to the diffraction limit, and for that purpose, it is necessary to suppress the aberration of the optical system involved in the transmission to the Marechal standard or less. Specifically, the wavefront aberration is 0.0
It must be 7λ or less. Since the transmission light emitted from the LD1 spreads widely (NA is about 0.45), it is necessary to correct only the first incident lens 2 as an aspherical lens to correct the wavefront aberration.

Although the resin lens 2 is used here for the purpose of cost reduction, it is also possible to use a glass lens. Unlike the resin lens, the glass lens has an advantage that the focal length does not change even if the ambient temperature changes, and thus the actuator may be a biaxial actuator in the XY axis directions.

Next, a method of obtaining servo signals in the XY axis directions will be described with reference to FIG. However, FIG. 8 shows the light intensity distribution of the reflected light from the end face of the optical fiber 15 in the X-axis direction (or the Y-axis direction), that is, in the 1-axis direction on the two-divided light receiving element 6 ′. Since the apex of the convex surface 15a of the optical fiber 15 is processed so as to be the center of the core 15c, the light when the focused beam is applied to the center of the core 15c as shown in FIG. The intensity distribution is symmetrical.
When this is received by the two-division light receiving element 6 ', if it is arranged so as to receive the peak of the light intensity distribution on the division line, the difference between the light reception currents of the left and right divided cells becomes zero.

On the other hand, when the focused beam is deviated from the center of the core 15c to the left, the light intensity distribution becomes asymmetrical as shown in FIG. 7B, and therefore the difference in the light receiving current between the left and right divided cells. Is negative. On the other hand, when the focused beam is deviated to the right from the center of the core 15c, FIG.
As shown in, the difference between the light receiving currents of the left and right divided cells becomes positive.

Therefore, if the vertical axis is the difference signal of the light receiving currents of the left and right divided cells and the horizontal axis is the displacement of the focused beam from the core center, a graph called an S curve as shown in FIG. 9 is obtained. As shown in this graph, the servo circuit 43 can know the distance from the core center of the focused beam from the magnitude of the difference signal and the direction of the core center from the polarity of the difference signal. Therefore, according to the present embodiment, unlike the first conventional example 1, high-speed automatic control is possible. Since the X-axis and the Y-axis are orthogonal to each other, if there is a 4-division light-receiving element whose dividing lines are orthogonal to each other, a servo signal in the XY2-axis direction can be obtained. Next, a method of obtaining a servo signal in the Z-axis direction will be described. To do. For this, the focus error detection method of the optical disk device shown in Table 1 below can be used.

[0069]

[Table 1]

In this embodiment, the astigmatism method of the focus error detection methods shown in Table 1 is used. This is because the cylindrical lens 5 is placed in the optical path as shown in FIG.
Is arranged, the shape of the beam incident on the four-division light receiving element 6 ″ changes depending on the position of the disk (corresponding to the end face of the optical fiber 15 in the present embodiment) in the Z direction. Is.

That is, as shown in the figure, when the focused beam is in focus on the disc, the beam incident on the four-division light receiving element 6 '' has a circular shape. On the other hand, if the beam is farther than the focused state, the shape of the beam is a horizontally long ellipse, and if it is close, it is a vertically long ellipse. Therefore, a servo signal in the Z-axis direction can be obtained depending on the shape of the beam.

Specifically, the focus error signal (corresponding to the Z-axis servo signal in this embodiment) can be obtained by the four-division light receiving element 6 ″ and the arithmetic circuit 40 shown in FIG. Z
In order to increase the independence of the axis servo signal and the XY axis servo signal, it is necessary that the dividing line for obtaining the Z axis servo signal and the cylindrical lens 5 are arranged to be rotated by 45 degrees around the Y axis. Therefore, in such a detection mode, XYZ
In order to obtain the servo signals in the three-axis directions, the 8-division light receiving element PD6 as shown in FIGS. 2A and 2B is required as the multi-division light receiving element.

When the outputs of the light receiving cells indicated by a to h in FIG. 2 are a to h, the servo signals are X-axis servo signals XS.
Is expressed by the following equation (1).

XS = (a + b + h + g)-(c + d + e + f) (1) Further, the Y-axis servo signal YS and the Z-axis servo signal ZS are expressed by the following equations (2) and (3), respectively.

YS = (a + b + c + d)-(e + f + g + h) (2) ZS = (a + b + f + e)-(c + d + h + g) (3) In addition to the above configuration, the optical transmission / reception module of this embodiment is connected to the light emitting element LD1. There is provided a signal processing system that delays the input transmission data for the settling time of the servo mechanism or more, and stops the operation of the actuator 11 after the servo settling while maintaining the position of the lens 10 to be position controlled.

FIG. 12 shows the system configuration of this signal processing system. A delay 41 may be provided to delay the transmission data. For example, if the transmission speed of the optical transceiver module is 5
If 0 Mbps and the settling time of the servo mechanism are 60 ms, such a delay 41 can be realized by a 3 Mbit FIFO memory.

This signal processing system includes a signal detecting circuit 42, a servo circuit 43, and a sample hold circuit 44 in addition to the delay 41 and the LD 1, the optical branching elements 3 and 7, the PD 6, the lens 10 and the actuator 11. . The servo circuit 43, the sample hold circuit 44 and the actuator 11 constitute a servo mechanism.

The operation will be briefly described below. When a transmission signal is input as an external input, the signal detection circuit 42 detects its rising edge and operates the servo circuit 43 by using the detection signal as a trigger signal. The servo signal is applied to the servo circuit 43 from the PD 6 as described above, and this servo signal is delayed by the delay 41 by a time period in which the settling time of the servo mechanism is taken into consideration. Servo circuit 4
3 gives a control signal and a settling signal to the sample hold circuit 44. The sample hold circuit 44 takes in the control signal at the timing when the settling signal is input and outputs it to the actuator 11. The current value of the actuator 11 is kept constant by this control signal.

Therefore, according to this signal processing system, since the current value of the actuator 11 can be kept constant after the servo mechanism is settled, the actuator 11 can be maintained while the position of the lens 10 to be position controlled is kept after the servo settling. The operation of can be stopped. Here, the servo circuit 4
The settling judgment of No. 3 can be made by a timer having a built-in settling time or by the size of the error signal.

The optical transmission / reception module of this embodiment may have the system configuration shown in FIG. 13 instead of the system shown in FIG. The system shown in FIG. 13 has a system configuration in which received light is incident on the PD 9 when the operation of the servo mechanism is stopped and the servo mechanism is not operated during reception.

Also in this system, the transmission data input to the LD 1 is delayed for the settling time of the servo mechanism or more, and after the servo settling, the operation of the actuator 11 is stopped while maintaining the position of the lens 10 to be position controlled. Is taking. However, the operation start of the servo circuit 43 is different as described later.

As can be seen by comparing FIG. 13 and FIG. 12, this system includes the signal detection circuit 45 for detecting the fall of the transmission signal, the relay 46, the timer 47, the power supply 48 and the switch 49 in the system of FIG. It is configured by adding. Therefore, the parts corresponding to those in FIG. 12 are designated by the same reference numerals.

As described above, the actuator 11 stands still at a position where the helical spring 17 and gravity or frictional force are balanced, unless power is supplied as described above. If the optical components are arranged so that the received light enters the PD 9 in this state, the received light enters the PD 9 when the operation of the servo mechanism is stopped.

The inventor of the present invention relates to a servomechanism. At the time of transmission, it is necessary to make the transmitted light incident on a narrow region of the optical fiber 15 having a core diameter φ9.5 μm. Therefore, highly accurate positioning (that is, servo operation) is required. However, when receiving, the received light is P
It has been found that high-precision positioning (servo operation) is not necessary as long as it is incident on a wide area of D9 light receiving area φ75 μm.

As a specific example, the position accuracy of the actuator 11 at the time of transmission needs to be ± 0.5 μm, but since the position accuracy at the time of reception is ± 20 μm, the servo operation can be stopped at the time of reception. .

The operation of this system will be briefly described below. The operation when the transmission data is input to the external input is the same as in the case of the system of FIG. 12, and therefore the description is omitted here. However, in this system, the operation of the servo circuit 43 is started by the power supply to the servo circuit 43 instead of the above trigger signal.

That is, it can be judged that the input of the transmission data is completed if the transmission data is not input for a certain period of time. Therefore, a timer 47 for starting the time limit at the fall of the transmission data is provided for this. Good. Therefore, in the present system, when the signal detection circuit 45 detects the fall of the transmission signal, the detection signal is used as a trigger signal to start the timer time limit of the timer 47, and when the timer time limit is reached, an OFF signal is output to the relay 46. Then, the relay 46 turns off the switch 49.
As a result, the supply of electric power from the power source 48 to the servo mechanism, that is, the servo circuit 43, the sample hold circuit 44 and the actuator 11 is cut off, so that the operation of the servo mechanism is stopped.

(Embodiment 2) FIGS. 14 to 17 show Embodiment 2 of the optical transceiver module of the present invention. As shown in FIG. 14, the optical transceiver module includes an LD 51, a lens 52, and a BS 5 which are hermetically sealed in a can package.
3, lens 54, PD 55 hermetically sealed in a can package, lens 56, actuator 57 for finely adjusting lens 56 in the XYZ three-axis directions, and receptacle 5
8 and these parts are held on an optical base 59.

As shown in FIG. 15, the PD 55 is composed of a five-divided light receiving element composed of five divided cells a to e. More specifically, it is configured by a five-division light receiving element in which four light receiving cells a to d are evenly arranged around the center light receiving cell e.

Since the basic operation of this optical transceiver module is the same as that of the optical transceiver module of the first embodiment, only different points will be described below.

With the system configuration shown in FIG. 13 described above, the PD 6 can also serve as the PD 9. Therefore, in the second embodiment, the PD 55 is the PD 6 of the first embodiment.
And PD9, and BS7 is omitted.

In addition, in the second embodiment, the beam size method shown in Table 1 and FIG. 16 is adopted as the detection method for obtaining the servo signal in the Z-axis direction, and the cylindrical lens 5 of the first embodiment is also omitted. ing. Since the detection principle of the beam size method is shown in FIG. 16, the description is omitted here.

Since the method of obtaining the servo signals in the XY2-axis directions is the same as that of the first embodiment, the 5-division light receiving element shown in FIGS. 15A and 15B is required to obtain the XYZ 3-axis servo signals. Become.

When the outputs of the light receiving cells indicated by a to e in FIG. 15 are a to e, the respective servo signals are X axis servo signals XS.
Is expressed by the following equation (4).

XS = (a + e)-(b + d) (4) The Y-axis servo signal YS and the Z-axis servo signal ZS are expressed by the following equations (5) and (6), respectively.

YS = (a + b)-(e + d) (5) ZS = (a + b + d + e)-(c) (6) The light reception signal is obtained by (a + b + c + d).

(Embodiment 3) FIG. 17 shows Embodiment 3 of the optical transceiver module of the present invention.

The optical transceiver module of the third embodiment is different from the optical transceiver module of the first embodiment only in that a wavelength branching element (hereinafter referred to as BS) 67 is used as the optical branch element corresponding to BS7 of the first embodiment. Are different. The parts corresponding to those in the first embodiment are designated by the same reference numerals.

Here, in the third embodiment, the wavelength λ of the transmission light emitted from the LD1 is 1.3 μm, while the wavelength λ of the reception light emitted from the optical fiber 15 is 1.5 μm. , The wavelengths of both are different.

Next, the operation of this optical transceiver module will be described. The transmission light emitted from the LD1 is collimated by the lens 2 and enters the BS3. 10% for BS3
A reflective film is formed so as to reflect the light. Therefore, 90% of the light flux of the incident light goes straight and is incident on BS7 which is a wavelength branching element.

BS7 reflects light having a wavelength of 1.5 μm,
A dielectric multilayer film is formed so as not to reflect light having a wavelength of 1.3 μm. Therefore, 100% incident on BS7
The light flux of is incident on the lens 10. The incident light flux is condensed by the lens 10 and is incident on the optical fiber 15 fixed to the receptacle 12. There, as described above, Fresnel reflection is performed, so that a maximum of 4% of light is reflected.

The reflected light is reflected by BS3 via the opposite optical path, passes through the lens 4 and the cylindrical lens 5, and
The light is incident on the PD 6 composed of a divided light receiving element. When the calculation of the above formulas (1) to (3) is executed based on the photocurrent of each divided cell generated from the reflected light incident on the PD 6, it is possible to obtain the servo signals in the XYZ triaxial directions.

Based on the obtained servo signal, a servo circuit (not shown) finely adjusts the actuator 11 so that the focusing position of the lens 10 is aligned with the center of the core of the optical fiber 15.

On the other hand, the received light emitted from the optical fiber 15 is made into a parallel light flux by the lens 10 and the incident light flux becomes 1
00% is reflected by the BS 7, passes through the lens 8, enters the PD 9 as converged light, and is converted into a reception signal.

(Fourth Embodiment) FIGS. 18 and 19 show a fourth embodiment of the optical transceiver module of the present invention. Fourth Embodiment
The optical transmission / reception module is characterized in that one hologram element 81 constitutes an optical branching element that divides the reflected light of the transmitted light at the end face of the optical fiber and an optical branching element that divides the transmitted / received light into two.

As shown in FIGS. 18 and 19, this optical transceiver module includes a can package 74 in which an LD 71, a light receiving element (PD) 72 and a multi-divided light receiving element (PD) 73 are hermetically sealed. Lens 75 and lens 75
An actuator 76 for finely adjusting the XYZ three-axis directions,
It is composed of a receptacle 77 and an optical base 78 for holding these components.

Next, the operation will be described. The transmission light emitted from the LD 71 passes through the cover glass 80 attached to the inner surface of the cap 79, and then the holographic optical element 81 attached to the outer surface of the cap 79 causes the 0th order light, the + 1st order light, and the −1st order light. Is divided into three diffused light fluxes. The three diffused light fluxes are converged by the lens 75, but only the 0th-order light thereof is fixed to the receptacle 77 in the optical fiber 82.
Incident on.

Since Fresnel reflection occurs here, the maximum is 4%.
Light is reflected. The reflected light goes through the optical path opposite to the above,
The holographic optical element 41 causes 0th order light, + 1st order light, -1
It is divided into three convergent light beams of the next light. Of these, the + 1st order light enters the PD 72 and the −1st order light enters the PD 73.

The calculations shown in the equations (4) to (6) are performed based on the photocurrent of each divided cell generated from the reflected light incident on the PD 33. This makes it possible to obtain servo signals in the XYZ triaxial directions. Then, based on this servo signal, a servo circuit (not shown) finely adjusts the actuator 76 so that the focus position of the lens 75 is aligned with the core center of the optical fiber 82.

On the other hand, the received light emitted from the optical fiber 82 is made into a convergent light flux by the lens 75, diffracted by the holographic optical element 41 as + 1st-order light, incident on the PD 32, and converted into a received signal.

[0111]

As described above, according to the optical transmitting and receiving module of the present invention, the optical branching element for dividing the transmitted light and the received light into two and the light receiving element for detecting the received light are provided. Two-way communication using is possible. Therefore, it can be applied to the PDS system.

According to the optical transceiver module of the third aspect, in particular, since the tip of the optical fiber, that is, the end face thereof is processed into a curved surface consisting of a concave surface or a convex surface, the incident angle to the optical fiber is transmitted light. It changes depending on the light collecting position of. Therefore, the reflectance apparently continuously changes depending on the condensing position, and the direction and the moving distance can be known. As a result, the servo settling time can be shortened.
Moreover, since the transmittance does not deteriorate even if the surface of the core of the optical fiber is processed, the light utilization efficiency is high. In addition, since the center of the optical fiber is the apex of the core, the amount of reflected light can be directly known, so that the servo accuracy can be improved.

According to the optical transmission / reception module of the fourth aspect, the actuator is caused to perform the servo operation based on the input transmission data, and the transmission data input to the light emitting element is delayed by the servo settling time or more. And after the servo settling, because the configuration of stopping the operation of the actuator while maintaining the position of the lens or optical fiber of the position control target, because the servo mechanism has completed the servo settling when the data is input to the light emitting element, No spill of transmitted data occurs. In addition, even if the transmission signal is incident on the multi-segment light receiving element, the actuator maintains the set position, so that the servo operation becomes unstable even if the transmission signal overlaps the light reception signal of the multi-segment light receiving element during signal transmission. It never happens. Furthermore, since the actuator is temporarily stopped and the current flowing through the servo circuit can be reduced, power consumption can be saved.

In particular, according to the optical transceiver module of the fifth aspect, the optical system is arranged so that the received light enters the light receiving element when the operation of the actuator is stopped, and the actuator is kept in the stopped state at the time of reception. Therefore, since the reflected light from the end face of the optical fiber does not enter the multi-divided light receiving element, the received signal can be correctly received.

Further, according to the optical transceiver module of the sixth aspect, since the multi-divided light receiving element also serves as the light receiving element, an inexpensive optical transceiver module can be realized.

Further, according to the optical transmitter / receiver module of the seventh aspect, since the first optical branching element and the second optical branching element are formed by one hologram optical element, the optical transmitter / receiver module is inexpensive. Can be realized.

Further, according to the optical transceiver module of the eighth aspect, since the wavelength branching element is used as the second optical branching element, the transmitting light of 1.3 μm and the receiving light of 1 called the ATM-PDS system are used. It can support wavelength multiplexing communication of 0.5 μm.

[Brief description of drawings]

FIG. 1 is a schematic side view showing a first embodiment of an optical transceiver module of the present invention.

2A is a plan view showing a cell structure of the multi-divided light receiving element of Embodiment 1, and FIG. 2B is a plan view showing another example of the cell structure.

FIG. 3 is a cross-sectional view showing the structure of the receptacle according to the first embodiment.

4A is a sectional view showing the optical fiber of Embodiment 1 together with a ferrule, and FIG. 4B is a sectional view showing another example of the optical fiber together with a ferrule.

FIG. 5 is a perspective view showing a partially broken structure of the actuator according to the first embodiment.

FIG. 6 is a perspective view showing another example of the actuator.

FIG. 7 is a sectional view showing another example of an optical fiber together with a ferrule.

8A to 8C are views for explaining a method of obtaining a servo signal in the XY axis directions in the optical transceiver module according to the first embodiment.

FIG. 9 is a graph showing an S curve of a servo signal in the XY axis directions, where the vertical axis represents the difference signal and the horizontal axis represents the displacement.

FIG. 10 is a diagram showing the optical transmission / reception module according to the first embodiment, Z
The figure for demonstrating the method of obtaining the servo signal of an axial direction.

FIG. 11 is a diagram for explaining a method of obtaining a servo signal in the Z-axis direction.

FIG. 12 is a block diagram of a system in which transmission data input to an LD, which is a light emitting element, is delayed for a settling time of a servo mechanism or more, and after the servo settling, the operation of an actuator is stopped while maintaining the position of a lens whose position is to be controlled.

FIG. 13 is a block diagram of a system in which components are arranged such that received light enters a PD when the operation of the servo mechanism is stopped, and the servo mechanism is not operated during reception.

FIG. 14 is a schematic side view showing a second embodiment of the optical transceiver module of the present invention.

15A is a plan view showing a cell structure of the multi-divided light receiving element of Embodiment 2, and FIG. 15B is a plan view showing another example of the cell structure.

FIG. 16 is a schematic diagram illustrating an optical transceiver module according to a second embodiment in which Z
The figure for demonstrating the method of obtaining the servo signal of an axial direction.

FIG. 17 is a schematic side view showing a third embodiment of the optical transceiver module of the present invention.

FIG. 18 is a side sectional view showing a fourth embodiment of the optical transceiver module of the present invention.

FIG. 19 is an enlarged side sectional view showing the can package of FIG.

FIG. 20 is a system configuration diagram showing a PDS system.

FIG. 21 is a side sectional view showing a first conventional example of an optical transceiver module.

FIG. 22 is a schematic side view showing a second conventional example of the optical transceiver module.

FIG. 23 is a perspective view showing an optical fiber.

FIG. 24 is a sectional view of an optical fiber.

FIG. 25 is a diagram for explaining a problem of the second conventional example.

[Explanation of symbols]

1,51 Semiconductor laser device (LD) 2,4,8,10,52,54,56,74 lens 3,7,53 Optical branching element (BS) 5 Cylindrical lens 6,55 Multi-divided photo detector 9 Light receiving element 10 lenses 11,57,76 Actuator 12,58,77 Receptacle 13,59,78 Optical Base 14 Ferrule 15,82 optical fiber 15a Convex surface formed on end face of optical fiber 15b Concave surface formed on end face of optical fiber 15c Optical fiber core 41 delay 42 Signal detection circuit 43 Servo circuit 44 Sample and hold circuit 45 Signal detection circuit 46 relay 47 timer 48 power 49 switch 67 Wavelength splitter 81 Hologram element

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI H04B 10/14 10/24 (58) Fields investigated (Int.Cl. ⁷ , DB name) H04B 10/00-10/28 H04J 14/00-14/08 G02B 6/42 G02B 13/00

Claims (7)

(57) [Claims] 1. An optical transmission / reception module for performing bidirectional communication by using a single optical fiber for both transmission and reception, wherein a light emitting element that emits transmission light and a reflection light at the end face of the optical fiber through which the transmission light is guided are provided. A first light splitting element that divides the light into two, a multi-divided light receiving element that receives the reflected light from the end face of the optical fiber, and a second light splitting element that is arranged between the light emitting element and the optical fiber and divides the transmitted and received light into two. Optical branching element, a light receiving element for receiving received light, a lens for condensing transmitted / received light, and an actuator for performing a servo operation for moving the lens or the optical fiber in at least two axial directions orthogonal to the optical axis.
And the tip of the optical fiber is added to a curved surface consisting of a concave surface or a convex surface.
The amount of reflected light of the transmitted light at the end face of the optical fiber
The multi-division reception that changes depending on the focus position of the transmitted light
It is detected by the optical element and based on the detection signal of the multi-divided light receiving element
An optical transceiver module that causes the actuator to perform a servo operation . 2. The optical transceiver module according to claim 1, wherein the actuator is an actuator that performs a triaxial servo operation that moves the lens or the optical fiber in an optical axis and in two axial directions orthogonal to the optical axis. 3. The actuator is caused to perform a servo operation based on input transmission data, the transmission data input to the light emitting element is delayed by a servo settling time or more, and after the servo settling, the position control target is moved. lens or an optical transceiver module according to claim 1 or claim 2 stops the operation of the actuator while maintaining the position of the optical fiber. 4. The first light receiving element is configured so that the received light enters the light receiving element when the servo operation of the actuator is stopped .
The optical transceiver module according to any one of claims 1 to 3 , wherein two optical branching elements are arranged and the actuator is kept in a servo operation stopped state during reception. 5. The optical transceiver module according to claim 1, wherein the multi-divided light receiving element also serves as the light receiving element. 6. The optical transceiver module according to claim 1, wherein the first optical branching element and the second optical branching element are formed by one hologram optical element. 7. The optical transceiver module according to claim 1, wherein the second optical branching element is a wavelength branching element.