JP4017944B2 - Optical communication device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a configuration of an optical communication device.
[0002]
[Prior art]
An optical communication device is a device for transmitting light, which is emitted by a semiconductor laser (hereinafter referred to as LD) and modulated by information, to an optical fiber. It consists of optical parts such as fiber. In an optical communication module used as an optical network unit (ONU) that draws optical fiber communication into a subscriber premises, in general, in order to support bidirectional communication in which transmission / reception is performed using a single optical fiber, The optical communication module further includes a light receiving element, a WDM (Wavelength Division Multiplex) filter for separating light of different wavelengths, and the like.
[0003]
In such an optical communication module, an LD, a lens, etc. must be positioned with high accuracy with respect to an optical fiber having a core diameter of several μm. Therefore, usually, these optical components are welded or used with an adhesive. It is firmly fixed.
[0004]
However, even if the optical communication module is configured by positioning and fixing the mutual positions of the components with high accuracy using an adhesive, the following problems remain. First, when an optical communication module is manufactured in this way, the quality of a product can only be determined after being bonded and dried. In addition, it is considered relatively difficult to achieve a high yield with such an optical communication module. Second, it is impossible to correct the performance when there is a change over time.
[0005]
Further, in the optical communication module, there is a possibility that optical communication with high accuracy may not be performed if the amount of light from the LD decreases with time. Therefore, it is necessary to control the amount of light so that the amount of light from the LD can always be kept constant.
[0006]
[Problems to be solved by the invention]
In view of the above circumstances, the configuration of an optical communication module that can maintain high performance without being affected by environmental changes including changes in mechanical conditions such as vibration, changes in ambient temperature, changes over time, etc., that is, the configuration of an optical communication device Is desired. That is, an object of the present invention is to provide an optical communication apparatus that can maintain performance even when there is an environmental change.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides an optical communication apparatus for transmitting signal light including information, a laser light source for emitting signal light, and directing the signal light from the laser light source to an optical fiber. And a lens for focusing the light and an actuator for moving the lens, a light deflecting means for guiding the signal light from the laser light source to the core center of the optical fiber, and the light of the signal light deflected by the light deflecting means First control means for performing negative feedback control on the light deflecting means so that the position in the incident surface to the fiber is guided to the center of the core, and APC for the laser light source so that the light quantity of the signal light becomes a predetermined light quantity. A second control means for controlling, a take-out means for taking out a part of the laser light guided by the light deflecting means and introduced into the optical fiber, and taken out by the take-out means; A first detecting means for periodically finely oscillating the lens via an actuator within the plane of incidence of the signal light on the optical fiber. Negative feedback control is performed by wobbling the position and comparing the light amounts of part of the laser light detected at two time points that are the maximum amplitude of the wobbling.
[0008]
According to the first aspect of the present invention, the negative feedback control is performed on the light deflecting unit so that the position of the signal light on the incident surface of the optical fiber is guided to the center of the core by the first control unit, and the second control unit performs the second feedback control. The control means performs light amount control on the laser light source, that is, APC control so that the signal light for transmission becomes a predetermined light amount. With such a configuration, it is possible to maintain the performance of the optical communication device while avoiding the influence of environmental changes.
[0009]
Here, the second control means executes the APC control by the second control means after making the signal light accurately guided to the core center by the negative feedback control by the first control means (claim). Item 2).
[0010]
According to the second aspect of the invention, it is possible to perform APC control with higher accuracy, and it is possible to emit a predetermined amount of signal light optimal for information transmission from the laser light source.
[0011]
First control means, by controlling the driving of the light deflecting means, the position in the plane of incidence of the optical fiber of the optical signal, so as to wobbling at a first frequency lower than the frequency of the transmission band of the signal light It is appropriate to adopt a simple configuration (claim 3).
[0012]
Since the frequency of the light amount change for negative feedback control detected by the light detection means is lower than the frequency of the transmission band, and thus can be identified, negative feedback control and signal transmission can be performed simultaneously. .
[0013]
Second control means, it is desirable to detect a signal for APC control frequency for lower APC control than the first frequency (Claim 4). With this configuration, APC control can be performed without stopping the driving of the light deflection unit. That is, it is possible to keep the light quantity of the laser light at a predetermined amount while monitoring the position of the signal light deflected by the light deflecting means on the optical fiber on the incident surface toward the center of the core.
[0014]
The second control unit drives and controls the laser light source so that the light amount detected by the light detection unit becomes a predetermined light amount. In particular, when the APC control is performed while the light deflecting unit is being driven, the second control unit controls the drive of the laser light source so that the average value of the amount of light changed by driving the light deflecting unit becomes a predetermined value. (Claim 5 ).
[0015]
Examples of the extraction means can be configured to reflect a portion of the introduced laser beam into an optical fiber to form a half mirror within the optical fiber to direct the optical fiber outside (claim 6). With this configuration, the control unit can perform negative feedback control using a part of the laser light extracted by being reflected by the half mirror.
[0016]
Alternatively, the optical fiber has a fiber coupler as extraction means, and a part of the laser light deflected by the optical deflection means and introduced into the optical fiber is extracted by the fiber coupler. With such a configuration, the control means can perform negative feedback control using a part of the laser light extracted by the fiber coupler (claim 7 ).
[0017]
In the present invention, when the above-described negative feedback control and APC control are performed using signal light for optical communication, a surface emitting laser that emits laser light from only one surface is used as a laser light source. (Claim 8) .
[0018]
In addition, since the surface emitting laser has a small emission angle of several degrees, there is an advantage that the arrangement accuracy of the components in the optical axis direction can be reduced.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram illustrating a configuration of an optical communication module 10 as a first embodiment of the present invention. The optical communication module 10 is used as an ONU that draws optical fiber communication into a subscriber's home. For example, a single optical fiber transmits a wavelength of 1.3 μm as an upstream signal and receives a signal of 1.5 μm as a downstream signal. This is an optical communication module that supports bidirectional WDM transmission. In FIG. 1, the solid line arrows represent upstream signal light, and the dashed arrows represent downstream signal light.
[0020]
A laser LD1, which is a light source of signal light for transmission, is a surface emitting laser, and is configured to be modulated by information for transmission. The laser LD 1, the condensing lens 3, the WDM filter 5, and the optical fiber 7 are arranged on a common optical axis, and the transmission light having a wavelength of 1.3 μm emitted from the laser LD 1 is transmitted through the optical fiber 7 by the condensing lens 3. The light is condensed toward the incident surface 7a. The WDM filter 5 passes the transmission light having a wavelength of 1.3 μm incident from the laser LD 1 toward the optical fiber 7.
[0021]
On the other hand, the received light having a wavelength of 1.5 μm transmitted through the optical fiber 7 is reflected by the WDM filter 5 and enters the photodetector 8 that receives the downstream signal light. The received light is converted to an electrical signal by the photodetector 8 and then processed to decode the information.
[0022]
As shown in FIG. 1, a half mirror 11 is formed on the optical fiber 7, and part of the signal light for transmission incident from the incident surface 7 a is reflected by the half mirror 11 and travels toward the photodetector 9. The optical communication module 10 detects the signal light for transmission incident on the optical fiber 7 with the photodetector 9. As a result, negative feedback control relating to the position of the signal light in the incident surface to the optical fiber 7 is performed so that the signal light is accurately guided to the center of the core, and control relating to the light amount of the signal light (APC control; Automatic Power Control) is performed to keep the amount of the signal light uniform to a predetermined amount.
[0023]
First, a configuration for negative feedback control of the position of signal light for transmission incident on the incident surface 7a of the optical fiber 7 will be described. The light detector 9 is connected to the controller 13, and the controller 13 is one of the signal light for transmission that is incident on the light detector 9, that is, reflected by the half mirror 11 and guided to the outside of the optical fiber 7. Get the light quantity of the part.
[0024]
FIG. 2 shows an example of a configuration for forming the half mirror 11 in the optical fiber. Thus, the half mirror part 23 can be provided in one optical fiber 21, and the other optical fiber 22 can be bonded via the adhesive layer 24.
[0025]
As shown in detail in FIG. 3, the controller 13 changes the position of the condenser lens 3 via the actuators 15 and 17, thereby changing the position of the signal light for transmission on the incident surface 7 a of the optical fiber 7. Can be changed. The actuator 15 can move the condenser lens 3 in one axial direction (X direction) in a plane perpendicular to the optical axis, while the actuator 17 moves the condenser lens 3 along the optical axis. It can be moved in the Y direction perpendicular to the X direction in a vertical plane.
[0026]
The controller 13 finely vibrates the condenser lens 3 in the X direction or the Y direction with a constant period and a constant amplitude, thereby changing the position of the transmission signal light on the incident surface 7a of the optical fiber 7 in the X direction or the Y direction. Can be vibrated slightly. In this way, the signal light is vibrated slightly, and then the change in the amount of the signal light for transmission that is reflected by the half mirror 11 and detected by the photodetector 9 is examined. The position of the signal light with respect to the core center on the incident surface 7 a of the optical fiber 7 is grasped, and thereby the signal light can be guided to the core center of the optical fiber 7. In the present specification, the operation of causing the signal light to vibrate slightly with a constant period and a constant amplitude in the X direction or the Y direction as described above will be referred to as “wobbling” hereinafter.
[0027]
The wobbling frequency is lower than the frequency of the transmission band of the signal light for transmission, and the two signals can be separated by adding an appropriate electrical frequency filter. Therefore, the controller 13 can take out the change in the light amount of the signal light for transmission due to wobbling even during the transmission of information with the signal light for transmission.
[0028]
The operation principle for obtaining the position of the transmission signal light relative to the center of the core 7c (core center 7d) in the incident surface 7a of the transmission signal light will be described in detail below with reference to FIGS. 4-7.
[0029]
FIG. 4 shows a cross-section of the incident surface 7a of the optical fiber 7 composed of the core 7c and the clad 7b, and indicates a wobbling operation in the incident surface 7a of the signal light for transmission (spot S) by a double arrow. Thus, in wobbling, the condenser lens 3 is vibrated at a constant period and constant amplitude in the X or Y direction. FIG. 4 shows a case where wobbling is performed in the Y direction.
[0030]
FIG. 4C shows a case where the position of the signal light for transmission in the incident surface 7a is the core center 7d, and FIG. 4B is slightly shifted to the plus side in the Y direction with respect to the core center 7d. 4A shows a case where the center of the core 7d is shifted more on the plus side in the Y direction than in the case of FIG. 4B. 4A, 4 </ b> B, and 4 </ b> C, symbol A (and symbol C) is a position in the incident surface 7 a of the current signal light for transmission (position when there is no movement due to wobbling), symbol B indicates a position when the wobbling is swung to the most minus side in the Y direction, and symbol D indicates a position when the wobbling is swung to the most plus side in the Y direction. That is, the position of the signal light for transmission in the incident surface 7a moves in the order of A → B → C → D → A by wobbling, and this operation is repeated as one cycle.
[0031]
FIG. 5 shows the amount of light detected by the photodetector 9, that is, the incident surface 7a of the optical fiber 7 when the position of the signal light for transmission in the incident surface 7a changes as shown in FIG. 4 due to wobbling. A change in the amount of signal light for transmission incident on the core 7c is shown. FIG. 5A shows a change in the amount of signal light for transmission when wobbling is performed in the state shown in FIG. 4A, and FIG. 5B shows the state shown in FIG. FIG. 5C shows the change in the amount of signal light for transmission when wobbling is performed. FIG. 5C shows the change in the amount of signal light for transmission when wobbling is performed in the state shown in FIG. Show.
[0032]
As shown in FIG. 5C, when the position of the transmission signal light in the incident surface 7a is the same as that of the core center 7d, the signal light is at the core center 7d at the position A, so that the maximum amount of light is obtained. At position B, the signal light is at the farthest position in the negative direction on the Y axis with respect to the core center 7d, so that the light quantity is minimum. At the position C, the signal light returns to the core center 7d, so that the maximum light amount is obtained again. At the position D, the signal light becomes the farthest position in the plus direction on the Y axis with respect to the core center 7d. It becomes.
[0033]
The light amounts of signal light for transmission detected by the photodetector 9 at the positions A, B, C, and D are Pa, Pb, Pc, and Pd, respectively. As is clear from FIG. 5C, when the position of the signal light for transmission in the incident surface 7a is the same as that of the core center 7d, the change in the amount of signal light due to wobbling is expressed by the following relationship (1). Can be defined by
Pb = Pd, Pa = Pc (1)
[0034]
Next, the signal light for transmission when the position of the signal light for transmission in the incident surface 7a is slightly shifted from the core center 7d to the Y axis plus side (FIG. 4B). The change in the amount of light is as shown in FIG. That is, at the position A, since it is slightly deviated from the core center 7d, it does not become the maximum light quantity, but coincides with the core center 7d at the position until it moves in the position B direction (reference numeral 81). Since the signal light moves away from the core center 7d from here to the position B, the light quantity of the signal light gradually decreases (reference numeral 82). It can be easily understood that the light amount changes from the position B to the position C along the reverse path to the light amount change from the position A to the position B.
[0035]
As the signal light moves further away from the core center 7d as it goes from the position C to the position D, the signal light quantity is further lowered and becomes the minimum light quantity at the position D. It can be easily understood that the light amount changes from the position D to the position A along a path opposite to the light amount change from the position C to the position D.
[0036]
As shown in FIG. 5B, when the position of the signal light in the incident surface 7a is slightly shifted from the core center to the Y-direction plus side, the waveform of the change in the amount of signal light when wobbling is performed is as follows. Compared with the waveform shape in the case of FIG. 5C, the light amount Pb at the position B is raised upward. Therefore, if the light amounts of signal light for transmission at position A, position B, position C, and position D in FIG. 5B are Pa, Pb, Pc, and Pd, respectively, the signal in the case of FIG. The change in the amount of light can be defined by the following relationship (2).
Pb> Pd, Pa = Pc (2)
[0037]
Next, when wobbling is performed in a state where the position of the signal light for transmission in the incident surface 7a is further shifted from the core center 7d to the Y axis plus side than in the case of FIG. 4B (FIG. 4A )), The change in the amount of signal light for transmission is as shown in FIG. That is, at the position A, the maximum light amount is not reached because the position A is deviated from the core center 7d. From position B to position C, a path opposite to the change in light amount from position A to position B is followed.
[0038]
As the signal light moves further away from the core center 7d as it goes from the position C to the position D, the signal light quantity further decreases and becomes the minimum light quantity at the position D. From position D to position A, a path opposite to the change in light amount from position C to position D is followed.
[0039]
In FIG. 5A, the light quantity Pb at the position B is larger than that in the case of FIG. If the light amounts of signal light for transmission at position A, position B, position C, and position D in FIG. 5A are Pa, Pb, Pc, and Pd, respectively, the signal light in the case of FIG. The change in the amount of light can be defined by the following relationship (3).
Pb >> Pd, Pa = Pc (3)
[0040]
From the relations (1), (2) and (3), the value obtained by subtracting Pb from Pd gradually decreases as the position of the signal light deviates from the core center 7d in the Y-axis plus direction (Pd−Pb It can be understood that the absolute value increases because the sign is negative.) Therefore, by using the result of (Pd−Pb) as a control signal, it is possible to perform negative feedback control with the position of the signal light directed toward the core center.
[0041]
However, it should be noted that the absolute value of (Pd−Pb) decreases on the contrary as the position of the signal light further shifts to the Y axis plus side from the state of FIG. If such a property is understood, it is possible to know the position of the core center 7d by appropriately changing the center position of the wobbling.
[0042]
The change in the amount of signal light due to wobbling described above with reference to FIGS. 4 (a) to 4 (c) and FIGS. 5 (a) to 5 (c) indicates that the position of the signal light is on the Y axis plus side from the core center 7d. It was a thing when it was shifted to. The case where the position of the signal light deviates from the core center 7d to the Y axis minus side is as follows. The definitions regarding the positions A, B, C, and D are the same as described above. The position A (and the position C) is the position in the incident surface 7a of the current signal light for transmission, and the position B is wobbling. The position D when swung to the most minus side in the Y direction is the position when swung most to the plus side in the Y direction due to wobbling. Due to wobbling, the position of the signal light for transmission in the incident surface 7a moves in the order of A → B → C → D → A.
[0043]
When the position of the signal light is slightly shifted to the Y axis minus side with respect to the core center 7d (when the position is opposite to the case of FIG. 4B across the core center 7d), the signal light is positioned. As it moves away from the center of the core as it moves from A to position B, the amount of signal light gradually decreases and becomes the minimum amount of light at position B. In the movement from the position B to the position C, the signal light quantity changes along the reverse path from the position A to the position B. In the middle of moving from position C to position D, the signal light coincides with the center of the core and thus becomes the maximum light quantity, and the signal light quantity decreases from that position toward position D. In the movement from the position D to the position A, the signal light amount changes along a path reverse to the position C → the position D.
[0044]
That is, the change in the signal light quantity in this case has a shape in which the waveform in FIG. 5B is shifted leftward in FIG. 5B by a time corresponding to 1/2 of the period T. The waveform of the change in light quantity in this case is shown in FIG. If the light amounts of signal light for transmission at position A, position B, position C, and position D in FIG. 6B are Pa, Pb, Pc, and Pd, respectively, the signal light in the case of FIG. The change in the amount of light can be defined by the following relationship (4).
Pb <Pd, Pa = Pc (4)
[0045]
Next, when the position of the signal light is further shifted to the Y axis minus side with respect to the core center 7d (when facing the case of FIG. 4A across the core center 7d), wobbling. The change in the signal light quantity due to is as follows. As the signal light moves from the position A to the position B, it moves away from the center of the core, so that the signal light quantity gradually decreases and becomes the minimum light quantity at the position B. In the movement from the position B to the position C, the signal light quantity changes along the reverse path from the position A to the position B. As the signal light moves from the position C to the position D, the signal light approaches the core center and substantially coincides with the core center at the position D. Therefore, the signal light quantity gradually increases and becomes the maximum light quantity at the position D. In the movement from the position D to the position A, the signal light amount changes along a path reverse to the position C → the position D.
[0046]
That is, the change in the signal light quantity in this case has a shape in which the waveform in FIG. 5A is shifted leftward in FIG. 5A by a time corresponding to 1/2 of the period T. FIG. 6A shows the waveform of the change in light quantity in this case. If the light amounts of signal light for transmission at position A, position B, position C, and position D in FIG. 6A are Pa, Pb, Pc, and Pd, respectively, the signal light in the case of FIG. The light quantity change can be defined by the following relationship (5).
Pb << Pd, Pa = Pc (5)
[0047]
From the above relations (4) and (5), it can be understood that the value obtained by subtracting Pb from Pd gradually increases as the position of the signal light shifts from the core center 7d to the Y axis minus side. That is, when the position of the signal light is shifted from the core center 7d to the Y axis minus side, the value of (Pd−Pb) is opposite to the sign when the position of the signal light is shifted from the core center 7d to the Y axis plus side. It becomes the value made.
[0048]
By examining the (Pd−Pb) code, it is possible to know whether the position of the signal light is shifted to the plus side or the minus side of the Y axis (or X axis) with respect to the core center. It also means that it is possible to know how much the position of the signal light is with respect to the core center by examining the absolute value of (Pd−Pb).
[0049]
Although the above description is the content when the position of the signal light is negatively feedback-controlled by wobbling in the Y-axis direction, the operation in the X-axis direction can be executed on the same principle.
[0050]
Based on the above facts, wobbling is performed in the Y-axis direction (or X-axis direction) to obtain the change in the amount of signal light, and the value (Pd−Pb) obtained based on the result and the core of the position of the signal light The correspondence relationship with the deviation with respect to the center can be represented by the graph of FIG. In FIG. 7, the horizontal axis represents the position shift around the core center 7 d of the position of the signal light, and the vertical axis is the value of (Pd−Pb).
[0051]
As described above, when the deviation of the position of the signal light with respect to the core center increases from 0 on the Y axis (or X axis) in the plus direction (right direction in FIG. 7), the sign of (Pd−Pb) is minus. The absolute value gradually increases and reaches the maximum value, and then decreases again to zero. On the contrary, when the deviation of the position of the signal light with respect to the core center increases from 0 to the minus direction (left direction in FIG. 7), the sign of (Pd−Pb) becomes plus, and the absolute value gradually increases and becomes the maximum value. After that, it decreases again and becomes zero.
[0052]
As shown in the timing chart of FIG. 8, when performing two-dimensional wobbling, wobbling is performed in the X-axis direction to detect (sample) the amount of signal light, and signal light for transmission in the X-axis direction is detected. During the feedback control of the position, the state is held with respect to the position of the signal light in the Y-axis direction, and the signal light amount detection (sampling) in the Y-axis direction is performed to perform the feedback control of the position of the signal light for transmission. While performing, it is appropriate to perform the sampling and holding in the X direction and the Y direction alternately, such as holding the state with respect to the position of the signal light in the X axis direction.
[0053]
Note that the negative feedback control operation as shown in FIG. 8 is configured to always be performed when the optical communication module 10 is used under severe environmental conditions in which vibration is always applied. However, it may be executed periodically when only consideration is required. During the negative feedback control operation and the negative feedback control operation, that is, while the negative feedback control operation is not performed, both the X and Y directions are maintained in the hold state.
[0054]
As described above, by extracting (Pd−Pb) from the light amount change of the signal light obtained by wobbling, the position of the signal light with respect to the core center can be acquired, and the signal light can be guided to the core center. . By performing two-dimensional wobbling in the X direction and the Y direction, the signal light is accurately guided to the core center.
[0055]
Next, a configuration for performing APC control on the amount of signal light for transmission incident on the incident surface 7a of the optical fiber 7 will be described. The APC control related to the signal light is performed after the operation of the negative feedback control related to the incident position of the signal light on the incident surface 7a is completed, that is, in a state where the signal light is accurately guided to the core center.
[0056]
As shown in FIG. 1, the photodetector 9 is connected not only to the controller 13 but also to the APC circuit 14. That is, in the optical communication module 10, the light detector 9 for performing the negative feedback control regarding the position and the light detector for performing the APC control are shared by the light detector 9. Thereby, the number of parts is reduced, and the structure is inexpensive and simple. The APC circuit 14 acquires the amount of light incident on the photodetector 9, that is, the amount of signal light for transmission reflected by the half mirror 11. The APC circuit 14 performs APC control of the laser LD1 so that the light amount of the signal light incident on the photodetector 9 is maintained at a predetermined light amount.
[0057]
In the present embodiment, APC control is performed without stopping wobbling. In this case, the average value of the amount of light that changes due to wobbling is used as a detection signal for APC control. The frequency that the APC circuit 14 performs APC control based on the detection signal is performed using a band lower than the wobbling frequency band. For example, this is an effective means when the optical communication module 10 is used under severe environmental conditions. Note that when the environmental conditions for using the optical communication module 10 are relatively mild, the condensing lens 3 is held in a state in which signal light is guided to the core center without performing wobbling by the controller 13 during APC control. May be.
[0058]
As described above, the optical communication module 10 is configured to detect the signal light passing through the optical fiber 7 and perform APC control. In addition, since the APC control is performed in a state where the signal light is accurately guided to the center of the core by negative feedback control of the incident position in advance, more accurate APC control is possible.
[0059]
FIG. 9 is a diagram showing a configuration of an optical communication module 40 as the second embodiment of the present invention. The optical communication module 40 is different from the optical communication module 10 of FIG. 1 in the configuration for extracting part of the signal light for transmission guided into the optical fiber. That is, the fiber coupler 41 is provided in the optical fiber 47, and a part of the signal light for transmission emitted from the laser LD1 is branched through the fiber coupler, and the light quantity is detected by the photodetector 9. ing. In FIG. 9, the same reference numerals are used for components equivalent to those of the optical communication module 10 of FIG.
[0060]
As described above, even when the fiber coupler 41 is used, a part of the signal light for transmission can be extracted as in the case where the half mirror 11 is used in FIG. Therefore, the optical communication module 40 achieves negative feedback control related to the incident position of the signal light with respect to the optical fiber 7 and APC control related to the amount of the signal light, as in the optical communication module 10.
[0061]
FIG. 10 shows a general example of the configuration of the fiber coupler 41. As shown in FIG. 10A, the fiber coupler 41 is formed so that the cores are adjacent to each other, and the cross section in the A1 direction in the figure has a shape as shown in FIG. A part of the signal light from the laser LD1 is coupled to the other core formed adjacently, whereby a part of the signal light from the laser LD1 is guided to the photodetector 9.
[0062]
There can be various configurations for extracting part of the signal light for transmission once guided into the fiber, so that an optical communication module is configured by appropriately replacing the half mirror and the fiber coupler according to these configurations. It is possible.
[0063]
Also, as signal light used for negative feedback control relating to position and APC control relating to light quantity, it is appropriate to take out the light once introduced into the fiber, but it is detected as the incident position on the optical fiber. If the correspondence relationship between the amounts of light is appropriately determined, it can be similarly implemented by receiving and using the signal light before entering the optical fiber.
[0064]
【The invention's effect】
As described above, according to the present invention, it is possible to perform negative feedback control so that the position of the signal light for transmission on the incident surface of the optical fiber becomes the center of the core, and the light amount of the signal light is always constant. APC control can be performed so that The optical communication apparatus configured to perform negative feedback control and APC control in this manner can maintain high performance without being affected by environmental changes.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of an optical communication module according to a first embodiment of the present invention.
FIG. 2 is a diagram showing an example of a configuration for forming a half mirror in an optical fiber.
3 is a diagram showing a configuration of an actuator for moving a condensing lens in the optical communication module of FIG. 1;
4A shows a wobbling operation when the position of the signal light for transmission in the incident surface 7a is shifted to the plus side in the Y direction with respect to the core center 7d. FIG. FIG. 4B shows the wobbling operation when the position of the signal light is shifted to the plus side in the Y direction with respect to the core center 7d by a smaller amount than in the case of FIG. 4A. FIG. The operation of wobbling when the position of the signal light is the core center 7d is shown.
5 (a), (b), and (c) show changes in the amount of signal light when the wobbling operation is performed as shown in FIGS. 4 (a), (b), and (c), respectively. It is a graph which shows.
6A shows the change in the amount of signal light due to wobbling when the position of the signal light is at a position opposite to the position of the core center 7d compared to the position in the case of FIG. 5A. FIG. FIG. 6B is a graph showing a change in the amount of signal light due to wobbling when the position of the signal light is at a position opposite to the core center 7d as compared with the case of FIG. 5B. is there.
FIG. 7 is a graph showing a correspondence relationship between a value of (Pd−Pb) obtained based on a result of obtaining a light amount change of signal light by performing wobbling and a deviation of the position of the signal light from the core center. is there.
FIG. 8 is a timing chart showing an operation when performing two-dimensional wobbling.
FIG. 9 is a diagram showing a configuration of an optical communication module as a second embodiment of the present invention.
10 is a diagram showing a general example of the configuration of a fiber coupler in the optical communication module of FIG.
[Explanation of symbols]
3 Condensing Lens 5 WDM Filter 7 Optical Fibers 8 and 9 Photodetector 10 Optical Communication Module 11 Half Mirror 13 Controller 14 APC Circuit

Claims (8)

An optical communication device for transmitting signal light including information,
A laser light source for emitting the signal light;
An optical deflector for guiding signal light from the laser light source toward an optical fiber and an actuator for moving the lens, and for guiding the signal light from the laser light source to the core center of the optical fiber Means,
First control means for performing negative feedback control on the light deflecting means so that the position of the signal light deflected by the light deflecting means in the entrance surface to the optical fiber is guided to the center of the core;
Second control means for performing APC control on the laser light source so that the light amount of the signal light becomes a predetermined light amount;
A take-out means for taking out a part of the laser light guided by the light deflecting means and introduced into the optical fiber;
A light detection means for detecting a light amount of a part of the laser light extracted by the extraction means,
The first control means periodically finely vibrates the lens via the actuator to wobbling the position of the signal light in the incident surface to the optical fiber, and two wobbling maximum amplitudes. An optical communication apparatus characterized in that the negative feedback control is performed by comparing a part of the amount of laser light detected at a time point. The optical communication device according to claim 1,
The second control means performs an APC control in a state where the signal light is guided to the center of the core by the negative feedback control. Said first control means, by driving and controlling the light deflection means, the position in the plane of incidence of the said optical fiber of said optical signal at a first frequency lower than the frequency of the transmission band of the signal light the optical communication apparatus according to claim 1 or claim 2, characterized in that cause wobbling. The optical communication apparatus according to claim 3, wherein the second control unit detects an APC control signal at a frequency for APC control lower than the first frequency.   The said 2nd control means drives and controls the said laser light source so that the average value of the said light quantity which changes when the said light deflection | deviation means drives becomes a predetermined value. 5. The optical communication device according to any one of 4.   2. The take-out means is a half mirror formed inside the optical fiber so as to reflect a part of the laser light introduced into the optical fiber and guide it to the outside of the optical fiber. The optical communication device according to claim 5.   6. The optical communication apparatus according to claim 1, wherein the extraction unit is a fiber coupler that branches out and extracts a part of the laser light introduced into the optical fiber.   The optical communication apparatus according to claim 1, wherein the laser light source is a surface emitting laser.

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