JP2006196568A - Apparatus and system for optical communication - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical communication apparatus which can achieve middle-distance half-duplex optical communication by using a light source for outputting nearly single wavelength without using optical components, such as a beam splitter or the like that is expensive and is necessary to be handled precisely. <P>SOLUTION: One surface emittive semiconductor laser 501 emits a light as a DC element at about 0.5 mW in a receiving state. An intense light of about 0.3 mW is given to the semiconductor laser 501 to disturb the light emission state thereof. As a result, the light emission intensity of the semiconductor laser 501 is reduced to around 0.1 mW. The change of the light emission intensity is received by an optical sensor 503. When the other optical communication equipment 511 is interrupted, the light emission intensity of the semiconductor laser 501 is enhanced, so that the light emission state of the semiconductor laser 502 is disturbed to convey interruption thereto. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a monitor light for keeping a light output at a predetermined value, a part of light emitted from a semiconductor laser, an optical communication apparatus using as an optical signal source, and an optical communication system.

  Semiconductor lasers are expected to be used for applications such as optical communications. In particular, the surface emitting semiconductor laser can emit laser light with a low threshold of, for example, about 1 mA, the light emitting surface is larger than the edge emitting semiconductor laser, and the coupling property with an optical system such as an optical fiber is good. Therefore, it is said to be suitable for optical communication at medium and short distances.

  It is known that surface emitting semiconductor lasers exhibit a phenomenon in which the light emission state is disturbed and the light emission intensity decreases when light is input during laser light emission. Usually, an optical system of a surface emitting semiconductor laser is used. Is formed so that light from the outside is not input.

  In addition, the surface emitting semiconductor laser drive circuit is, for example, a circuit configuration for correcting a change in the ambient temperature and a variation of the surface emitting semiconductor laser itself to keep the time average value of the light intensity at a predetermined value. It is necessary to have.

  In order to keep the time average value of the light intensity at a predetermined value, for example, a signal obtained by applying a part of light from the surface emitting semiconductor laser to the optical sensor for monitoring is processed, and the surface emitting semiconductor laser is processed. There is known a circuit configuration for controlling the current for driving the surface emitting semiconductor laser so that the time average value of the light intensity from the optical sensor becomes a predetermined value by feeding back to the current for driving the laser.

  By using this circuit, the time average value of the light intensity of the surface-emitting type semiconductor laser, whose light emission intensity is likely to become unstable due to factors such as temperature changes, can be maintained at a predetermined value, and information from the outside in a stable state. Can be transmitted and received using the intensity of light.

  Here, in order to reduce the cost required to improve the environment for sending and receiving information, two-way communication is possible using a single optical fiber, a single semiconductor laser, and a single optical sensor. It is effective to perform half-duplex communication, and several communication systems have been proposed to perform half-duplex communication.

  For example, as shown in Patent Document 1, two types of light sources having different emission wavelengths and a light detection system corresponding to the two types of light sources are used to realize half-duplex communication with a single optical fiber. It has been known.

  Further, as shown in Patent Document 2, a system that realizes half-duplex communication by resolving a collision state using a radio wave at the time of packet collision and restoring communication is known.

Japanese Patent Laid-Open No. 10-243006 (pages 3 to 8, FIGS. 1 and 10) JP 2002-271344 A (pages 4-6, FIG. 1)

  However, the system described in Patent Document 1 requires two types of light sources having two types of wavelengths and two types of optical sensors corresponding to the two types of wavelengths in order to perform half-duplex communication. In addition to the increase in the optical frequency, a separate optical bandpass filter that separates the light for each wavelength of light, such as a spectroscope, is required, the number of optical components increases, and adjustment that requires mechanical alignment is required. Since the number of locations increases, the reliability of the system is lowered in addition to the high cost.

  Moreover, in the system described in Patent Document 2, it is necessary to perform wireless communication in addition to light in order to eliminate the collision state using radio waves at the time of packet collision. For this reason, there is a problem in that wireless radio waves cannot reach between two terminals that are separated from each other, and communication cannot be performed.

  Therefore, the present invention does not use communication means other than light such as radio waves, does not use expensive optical components that require precise handling such as a beam splitter, and does not use a multi-wavelength light source. An object of the present invention is to provide an optical communication apparatus and an optical communication system that realize half-duplex optical communication.

  In order to achieve the above object, an optical communication apparatus according to the present invention includes a semiconductor laser of the local station, an optical sensor of the local station that receives a part of light from the semiconductor laser of the local station, and an optical sensor of the local station An optical communication device of the local station, which extracts a signal from the local station and drives the semiconductor laser of the local station, and another station optically coupled to the semiconductor laser of the local station Other station having substantially the same configuration as the optical communication device of the own station, comprising a semiconductor laser, an optical sensor of the other station that receives a part of light from the semiconductor laser of the other station, and a drive circuit of the other station (1) When receiving a signal from the optical communication apparatus of the other station using the optical communication apparatus of the own station, the semiconductor laser of the other station The low frequency specified by the time constant of the disturbance due to temperature change and aging, Driven to transmit a modulation signal having a high frequency defined by a shorter time constant, and the semiconductor laser of the local station is driven to maintain a weak laser emission state on a time average using the drive circuit of the local station In the case where weak light is incident on the semiconductor laser of the local station from the semiconductor laser of the other station, the laser emission state of the local station is not affected, and when strong light is incident, Using the phenomenon that the emission power of the semiconductor laser of the local station decreases due to disturbance of the laser emission state of the local station, the intensity of the emission intensity of the other station is changed to the intensity of the emission power of the semiconductor laser of the local station. When the emission intensity of the other station is weak, the emission output of the semiconductor laser of the local station becomes “weak”, and when the emission intensity of the other station is strong, it becomes “weak” which is weaker than weak. Light output of the local laser Of the output of the optical sensor of the local station that is received by the optical sensor of the local station and receives a part of the emission output of the semiconductor laser of the local station, the output is lower than the frequency of the modulation signal transmitted from the other station. The frequency component is treated as a disturbance component of the emission intensity of the semiconductor laser of the local station, the driving power of the semiconductor laser of the local station is controlled so as to be removed, and a high frequency equal to or higher than the frequency of the modulation signal transmitted from the other station Component is output as a signal from the optical communication device of the other station, and (2) when the signal from the optical communication device of the other station is transmitted using the optical communication device of the own station When interrupting the optical communication device of the above, by switching from a reception state that is driven to maintain a weak laser emission state on a time average to a strong laser emission state, the semiconductor laser of the other station is “strong” Send a signal, An interrupt occurs when the other station's semiconductor laser is in a “weak” state, which occurs when the driving state of the semiconductor laser of the other station is “weak”, and the optical sensor of the other station receives a “weak” light emission output. (3) When transmitting a signal to the optical communication device of the other station using the optical communication device of the local station, the local station and the other station of (1) are exchanged and executed. (4) When interrupting the other station while transmitting a signal from the optical communication apparatus of the other station using the optical communication apparatus of the own station, the own station and the other of (2) It is characterized in that it is executed by exchanging stations.

  According to this configuration, the signal output from the optical sensor of the local station is separated into a signal from another station having a high frequency component and a disturbance component of emission intensity due to the local station having a low frequency component. Thus, the signal transmitted from the other station and the signal for adjusting the automatic output of the semiconductor laser of the own station can be taken out from one optical sensor.

  If the optical communication device of the local station is used to interrupt the optical communication device of the other station when transmitting a signal from the optical communication device of the other station, the weak laser emission state is maintained on a time average. By switching from a receiving state that is driven to a strong laser emission state, a "strong" signal is transmitted to the semiconductor laser of the other station, and the driving state of the semiconductor laser of the other station is a "weak" state of a strong or weak signal If the light sensor in the other station receives a “weak” light output, it can be interrupted by determining that an interrupt has occurred. Duplex communication can be performed.

  In the above-described optical communication apparatus of the present invention, the light intensity in the weak state uses a phenomenon in which the light emission state of the semiconductor laser is disturbed that occurs when strong light is input from the other optical communication apparatus. When the strong light is input from the other optical communication device, the emission intensity is set to be lower than the weak state compared to the case where the strong light is not input from the another optical communication device. It is characterized by that.

  Within this weak state range, the strength of the optical signal from another optical communication device can be obtained as a signal whose strength is reversed due to the disturbance of the light emission state of the semiconductor laser.

  In the above-described optical communication apparatus of the present invention, the semiconductor laser is a surface emitting semiconductor laser.

  According to this configuration, the surface emitting semiconductor laser can easily align the optical system because the area of the light emitting / receiving region is wider than that of the edge emitting semiconductor laser.

  Further, the above-described optical communication system of the present invention includes two optical communication devices and performs half-duplex communication.

  By using this configuration, it is possible to obtain an optical communication system capable of performing half-duplex communication having the characteristics described above.

 DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, embodiments of the invention will be described with reference to the drawings.

<Embodiment 1>
1-1. Optical System of Optical Communication Device FIG. 1 is a cross-sectional view schematically showing an optical system of an optical communication device according to a first embodiment of the present invention. Hereinafter, the optical operation will be described using this cross-sectional view.

  The light emitted from the surface-emitting type semiconductor laser 101 mounted on the can package 107 including the stem 103 and the translucent plate 104 passes through the translucent plate 104, is collected by the condenser lens 105, and is collected on the optical fiber 106. Led. Here, when passing through the light transmitting plate 104 constituting the can package 107, a part of the light emitted from the surface emitting semiconductor laser 101 is reflected by the light transmitting plate 104 constituting the can package 107. Is incident on the optical sensor 102. In this way, the light emitted from the surface emitting semiconductor laser 101 is distributed to the optical fiber 106 and the optical sensor 102. In order to increase the amount of light incident on the optical sensor 102, a dielectric multilayer film having a higher reflectance than that of normal glass may be used for the light transmitting plate 104. Further, a material having an optical attenuator function for controlling the coupling efficiency with another optical communication device may be used in accordance with the characteristics of another optical communication device coupled through the optical fiber 106. In the present embodiment, a dielectric multilayer film having a reflectance of about 50% and a transmittance of about 50% is used for the light transmitting plate 104.

  Further, an optical attenuator (not shown) for controlling the coupling efficiency with another optical communication device between the optical fiber 106 and the condensing lens 105 or between the condensing lens and the light transmitting plate 104. May be inserted to adjust the light intensity from the outside.

  In addition, optical coupling between the optical fiber 106 and the surface emitting semiconductor laser 101 is performed only by the condensing lens 105, but this is a more advanced optical system, for example, a combined lens that can suppress astigmatism and the like. An aspherical lens (not shown) or the like may be used.

  For the optical sensor 102, a photodiode, a PIN photodiode, a phototransistor, an avalanche photodiode, or the like can be used. In particular, when a photodiode is used, a highly linear current signal that is substantially proportional to the number of photons is generated, so that the light intensity can be accurately known.

  In addition, when a PIN photodiode is used, the junction capacitance can be reduced in addition to the advantage of the high linearity of the photodiode, so that the photosensor is excellent in high-speed response.

  In addition, the phototransistor supplies an amplified current using the photocurrent obtained from the photodiode as a base current, and a large photocurrent can be obtained even when the light intensity is low. A highly sensitive optical sensor can be provided.

  Avalanche photodiodes generate avalanche phenomena of electrons based on the photocurrent obtained from the photodiode and multiply the photocurrent to obtain a signal. By using an avalanche photodiode, high speed, high An optical sensor having sensitivity characteristics can be provided.

1-2. Optical communication device circuit system (APC: automatic output control)
FIG. 2 is a circuit diagram for performing electrical processing by an operational amplifier using the optical system shown in FIG. Hereinafter, an electrical process for maintaining the direct current component of the light received by the optical sensor 102 at a predetermined value will be described with reference to this circuit diagram.

  As shown in FIG. 1, light reflected from the surface-emitting type semiconductor laser 101 by the light transmitting plate 104 constituting the can package 107 is incident on the optical sensor 102 of the optical block 100.

  The optical sensor 102 outputs a current substantially proportional to the received light intensity. This current is converted into a voltage signal by the resistor 207 according to Ohm's law.

  As shown in FIG. 2, the DC component of the signal converted into the voltage signal is applied to the non-inverting input of the OP amplifier 201 via the inductor 206, and the signal component passes through the capacitor 209. Applied to the inverting input of the OP amplifier 208. A reference voltage is applied to the inverting input of the OP amplifier 201. Note that an 8-16 modulation method in which a direct current component is sufficiently suppressed is used as a modulation method of light input from the outside. Accordingly, fluctuations in the DC level due to signal density are negligible, and external signal density does not cause an error in APC operation.

  Here, it will be described that the circuit shown in the figure performs an APC operation for stabilizing the direct current component of the emission intensity of the surface emitting semiconductor laser 101.

  Here, for the sake of simplification, a case where light from the outside is not incident will be described. However, as described above, the time average value of the optical signal injected from the outside becomes a substantially constant value. Since a modulation method or the like is used, the density of signals from the outside does not affect the APC operation, and the APC operation is performed in the same manner even when light from the outside is incident.

  For example, it is assumed that the direct current component of the emission intensity of the surface-emitting type semiconductor laser 101 is slightly increased due to a temperature change in the surroundings. When the direct current component of the emission intensity of the surface emitting semiconductor laser 101 increases, the light reflected by the light transmitting plate 104, which is a part of the laser light emitted from the surface emitting semiconductor laser 101, also increases. Therefore, the direct current output from the optical sensor 102 increases, and the direct current voltage generated in the resistor 207 increases. Then, the voltage applied to the non-inverting input of the OP amplifier 201 via the inductor 206 increases.

  Since the voltage applied to the non-inverting input of the OP amplifier 201 increases, the output of the OP amplifier 201 operates to supply a positive voltage.

  Since the output potential of the OP amplifier 201 is in the positive direction, a negative potential is applied, and the absolute value of the current applied to the surface emitting semiconductor laser 101 driven by a negative current decreases.

  Therefore, the direct current component of the emission intensity of the surface-emitting type semiconductor laser 101 is also reduced, and the voltage applied to the inverting input of the OP amplifier 201 and the voltage applied to the non-inverting input are operated to be equal. Be countered. Accordingly, a so-called APC operation is realized in which the direct current output of the surface emitting semiconductor laser 101 is controlled only by the reference voltage without receiving a factor such as a temperature change.

1-3. Optical communication device circuit system (receiving optical signals input from outside the optical communication device)
FIG. 1 is a cross-sectional view schematically showing an optical system of an optical communication apparatus. As shown in FIG. 1, an optical sensor 102 includes an optical signal from a surface emitting semiconductor laser 101 and an optical signal from the outside. Are superimposed and received and output as an electrical signal.

  FIG. 2 is a circuit diagram for performing an APC operation of the surface-emitting type semiconductor laser and performing an electrical signal processing to extract an externally intensity-modulated optical signal.

  FIG. 3 is a graph showing the time transition of the current waveform output from the optical sensor when external light is applied.

  Hereinafter, a method for extracting a signal when external light is applied will be described with reference to these drawings and graphs. In a state where there is no signal from the outside, the surface emitting semiconductor laser 101 is assumed to be held in a state where laser emission is performed in a direct current manner at 0.5 mW, for example.

  FIG. 3A shows a light intensity signal given to the surface emitting semiconductor laser 101 from the outside of the optical block 100 via the optical fiber 106 and the condenser lens 105 (see FIG. 1).

  The light intensity on the surface emitting semiconductor laser 101 is 0.05 mW in the low light amount state and 0.3 mW in the strong light amount state.

  3A, 3B, and 3C is time, and is synchronized between FIGS. 3A, 3B, and 3C.

  In FIG. 3A, the vertical axis indicates the light intensity that enters the optical block 100 via the optical fiber 106 and is supplied via the condenser lens 105. In FIG. It is illustrated. The vertical axis of FIG. 3B represents the light intensity of the laser output from the surface emitting semiconductor laser 101, and is indicated as L (LD). The vertical axis in FIG. 3C represents the intensity of the photocurrent output from the optical sensor 102 and is indicated as I (PD).

  In the low light amount state, the influence on the light emission state of the surface emitting semiconductor laser 101 is small, and the light emission state hardly changes. Therefore, the surface emitting semiconductor laser 101 outputs 0.5 mW of light as in the case where there is no signal from the outside.

  In the strong light quantity state, the influence on the light emission state of the surface emitting semiconductor laser 101 becomes significant, and the light emission output of the surface emitting semiconductor laser 101 decreases, for example, to 0.1 mW.

  FIGS. 3A and 3B are graphs showing the time transition of the influence of the light emission output of the surface-emitting type semiconductor laser 101 due to the intensity of light from the outside. The strong light from the outside is shown in the surface-emitting type semiconductor. It is shown that the light output of the surface emitting semiconductor laser 101 is reduced by inputting to the laser 101.

  FIG. 3C is a graph showing a temporal transition of a decrease in photocurrent generated in the optical sensor 102 due to a decrease in light output of the surface emitting semiconductor laser 101.

  As described above, it is shown that by inputting light from the outside to the surface-emitting type semiconductor laser 101 of the optical communication apparatus 200, a current output corresponding to another light intensity level can be obtained. When the input light intensity is a low light amount, for example, the output current of the optical sensor 102 decreases to 50 μA, and when the input light intensity is a high light amount, it decreases to 10 μA. The incoming optical signal can be received.

1-4. Optical communication device circuit system (suppression of fluctuations in optical sensor output caused by drive current modulation)
When the current applied to the surface-emitting type semiconductor laser 101 of the optical communication apparatus 200 is modulated to change the light intensity, the amount of light received by the optical sensor 102 also changes, so the current output of the optical sensor 102 also changes. Therefore, it is difficult to detect an externally received signal such as an interrupt in a state where an optical signal is being transmitted.

  Therefore, the fluctuation of the current output of the optical sensor 102 due to the modulation of the current applied to the surface emitting semiconductor laser 101 and the current applied to the surface emitting semiconductor laser 101 are calculated and canceled to detect a signal from the outside. It is necessary to do.

  Hereinafter, the fluctuation of the current output of the optical sensor 102 caused by the modulation of the current applied to the surface emitting semiconductor laser 101 will be described using the fluctuation of the current applied to the surface emitting semiconductor laser 101 with reference to FIGS. A method of canceling will be described.

  FIG. 4 is a graph showing the time transition of the current waveform output from the optical sensor when external light is applied.

  As shown in FIG. 2, the optical communication apparatus 200 drives the surface emitting semiconductor laser 101 by superimposing an OP amplifier 201 for determining a DC operating point to a constant value and a signal from a signal source 204. ing. The inductor 202 is a high cut filter for avoiding the inflow of the signal from the signal source 204 to the OP amplifier 201, and the capacitor 203 is a low cut filter for avoiding the inflow of a DC component from the OP amplifier 201.

  Next, the current signal generated by the signal source 204 is converted into a voltage by the variable resistor 205, further divided and input to the inverting input terminal of the OP amplifier 208.

  FIG. 4B is a graph showing the time transition of the drive current of the surface emitting semiconductor laser 101. FIG. 4A is a graph showing the time transition of the drive current of the surface emitting semiconductor laser 101.

  Next, the variable resistor 205 is adjusted in a state in which light from the outside is not entered, and adjustment is performed so that the modulation output does not substantially appear in the output of the OP amplifier 208. By this adjustment, the optical modulation signal that is an AC signal of the surface emitting semiconductor laser 101 is canceled by a substantial subtraction (described later) with the drive current signal, and is not detected as an optical signal. FIG. 4C shows the output waveform of the OP amplifier 208 after the cancellation, and it can be seen that the cancellation is almost complete except for the disturbance of the signal in the transient state. The resistor 212 adjusts the gain of the OP amplifier 208, and in this case, the gain is set to be about 10 times.

  As described above, the adjusted optical communication apparatus shown in FIG. 2 uses the surface emitting semiconductor laser 101 to convert the electric signal to the surface emitting type when the modulation format in which the average value of the AC component is substantially zero is used. Even if light intensity modulation is applied in addition to the semiconductor laser 101, the output of the OP amplifier 208 is in a state resulting from electric signal modulation.

  Note that the substantial subtraction between the light modulation signal and the drive current signal is that the surface emitting semiconductor laser 101 of this embodiment is driven by a negative current. The absolute value of the negative current that drives the semiconductor laser 101 increases, and the optical output of the surface-emitting type semiconductor laser 101 increases. Therefore, by adding the proportional coefficient K between the light intensity and the drive current by the resistors 210 and 211 (corresponding to the vertical axis I (PD) + KI (LD) in FIG. 4C or E)). This shows that a substantial subtraction between the light intensity and the drive current is performed.

1-5. Optical communication device circuit system (interrupt signal detection)
When the optical communication apparatus 200 is in a state of transmitting a signal to the outside, an operation called an interrupt is performed in order to temporarily stop transmission and move the optical communication apparatus 200 to a reception state in response to a request from the outside. It is necessary to do it.

  Here, the interrupt will be described with reference to FIGS.

  1-4. As shown in FIG. 5, even if an electric signal is given from the signal source 204 and the surface emitting semiconductor laser 101 is subjected to electric signal modulation, the output of the OP amplifier 208 is adjusted so that a signal due to the electric signal modulation does not appear. It is assumed that the optical communication apparatus 200 transmits an optical signal to the outside.

  In a state where there is no input light or the input light is small, for example, a light amount of about 0.05 mW, as shown in FIGS. 4A to 4C, the optical signal accompanying the fluctuation in the driving current of the surface emitting semiconductor laser 101 is It is suppressed and is not output as an output from the OP amplifier 208.

  On the other hand, in a state where the input light is large, for example, a light amount of about 0.3 mW, the light output of the surface emitting semiconductor laser 101 corresponds to the “high” level of the digital signal, and in a large state of about 3 mW, the influence is not so great. Although not received, the light output is affected by a small state of about 0.5 mW corresponding to the “low” level of the digital signal, and the waveform shown by the dotted line in FIG. 4D is output. The optical communication device 200 having an excellent SN ratio is obtained by setting the light intensity of the “low” level of the digital signal and the light intensity for receiving the signal to the same value that is highly sensitive to the input light intensity. Is obtained.

  The solid line in FIG. 4D is obtained by overwriting the waveform when the input light is small, and only the difference between the dotted line and the solid line is not canceled, and the waveform in FIG. 4E is the input current waveform of the OP amplifier 208. Therefore, it can be recognized that there was strong input light from the outside. The output of the OP amplifier 208 is obtained by multiplying the input current waveform and the value of the resistor 212 and inverting the sign (not shown).

  In this embodiment, the light intensity of the time average value on the receiving side is set to 0.5 mW. However, the present invention is not limited to this value. When receiving light from the outside, the light from the outside is in a strong state. In this case, it may be in a condition range in which the light output of the surface emitting semiconductor laser 101 decreases.

  The effects of the first embodiment will be described below.

  (1) The light intensity of the time average value of the surface emitting semiconductor laser 101 on the receiving side is 1-2. As shown in Fig. 5, it is kept in a weak state of about 0.5 mW using APC. 1-3. As shown in FIG. 4, when light is input from the outside to the surface emitting semiconductor laser 101, the phenomenon that the light intensity of the surface emitting semiconductor laser 101 becomes weaker than the weak state can be used independently of the APC operation. Since an optical signal from the outside is received, only one optical sensor 102 can be used to simultaneously perform an APC operation and an optical signal from the outside.

  (2) Since the light emitting region of the surface emitting semiconductor laser 101 is wider than that of the edge emitting semiconductor laser, the optical system can be easily aligned.

  (3) From the light intensity signal detected by the optical sensor 102, the value obtained by multiplying the current value driving the surface emitting semiconductor laser 101 by a proportional coefficient is canceled out, so that the surface emitting semiconductor laser 101 is converted from the light intensity signal. The drive current can be removed, and only the optical signal incident from the outside can be separated and detected.

  (4) Even in a transmission state in which the surface emitting semiconductor laser 101 performs light intensity modulation, when a strong optical signal from the outside, for example, light enters through the optical surface of the surface emitting semiconductor laser 101, the surface emitting semiconductor laser When the light emission state of 101 is “weak” of the strength signal, the light output is reduced. Therefore, even when the surface emitting semiconductor laser 101 is transmitting the light strength signal, the interrupt signal is transmitted. You can recognize what has been done.

<Embodiment 2>
2-1. Optical communication system for half duplex communication (Both reception waiting state)
Next, 1-1. -1-5. An optical communication system for performing half-duplex communication using the optical communication device described in 1 will be described. This optical communication system uses two optical communication devices 200 as shown in FIG. 5 and is arranged so that both can transmit and receive. In order to distinguish both, another number is given again.

  In the optical communication device 510 (200), part of the light output from the surface emitting semiconductor laser 501 is reflected by the light transmitting plate 507 and input to the optical sensor 503. The light transmitted through the light transmitting plate 507 is input to the optical fiber 509 through the condenser lens 505. The same operation is performed in the optical communication device 511 (200), and a part of the light output from the surface emitting semiconductor laser 502 is reflected by the light transmitting plate 508 and input to the optical sensor 504. The light transmitted through the light transmitting plate 508 is input to the optical fiber 509 through the condenser lens 506.

  First, when neither of the optical communication devices 510 and 511 transmits a signal, both the surface emitting semiconductor lasers 501 and 502 are held in a state of emitting light with low intensity. In this case, a structure is required in which the optical coupling efficiency is set to an appropriate value, for example, about 10% so that the mutual laser beams do not interfere with the other laser emission. In the present embodiment, the reflectance of the light transmitting plates 507 and 508 is set to about 50%. 50% of the light emitted from the surface emitting semiconductor laser 501 of the optical communication device 510 passes through the light transmitting plate 507, passes through the optical fiber 509, passes through the light transmitting plate 508, and emits light from the surface of the optical communication device 511. Is sent to the type semiconductor laser 502. Since it passes through such an optical path, the light intensity is attenuated to 50% × 50% = 25% due to reflection loss at the light transmitting plate 507 and the light transmitting plate 508. In addition to this, for example, a coupling loss with the optical fiber 509 and the like are also added, and thus strongly depends on the design of the optical system. In the optical system of the present embodiment, the reflectance of the light transmitting plate 507 and the light transmitting plate 508 is 50%. Thus, the optical coupling efficiency between the surface emitting semiconductor laser 501 and the surface emitting semiconductor laser 502 is set to about 10%.

  Here, although the optical coupling efficiency is about 10%, this is an example and is not limited to a value of about 10%. For example, the structure of the surface emitting semiconductor lasers 501 and 502, etc. In some cases, a coupling efficiency of 1% or less or a coupling efficiency of 30% or more is appropriate.

  The appropriate value of the light output of the surface emitting semiconductor lasers 501 and 502 in the low intensity state varies depending on the structure of the surface emitting semiconductor lasers 501 and 502, but a value of about 0.5 mW can be selected, for example. .

  Next, when the optical communication device 510 starts transmission of an optical signal, the surface emitting semiconductor laser 501 of the optical communication device 510 transmits light in a high intensity state and light in a low intensity state corresponding to the transmission signal to an optical fiber. Via 509, an optical signal is transmitted to the surface emitting semiconductor laser 502 of the optical communication device 511.

  Since the optical coupling efficiency between the surface emitting semiconductor laser 501 and the surface emitting semiconductor laser 502 is about 10%, the surface emitting semiconductor laser 501 of the optical communication apparatus 510 is in a weak intensity state of about 0.5 mW. In other words, light of about 0.05 mW is substantially incident on the surface emitting semiconductor laser 502. In this case, since the amount of light applied to the surface emitting semiconductor laser 502 is small, there is little influence on the light emission state of the surface emitting semiconductor laser 502, and the light emission state of the surface emitting semiconductor laser 502 of the optical communication device 511 does not change.

2-2. Optical communication system for half duplex communication (change from both reception waiting state to transmission / reception state)
The operation when the optical communication apparatus 510 is the transmission side and the optical communication apparatus 511 is the reception side will be described.

  First, the surface emitting semiconductor laser 501 of the optical communication apparatus 510 transmits a communication signal using, for example, two values of a strong intensity state of about 3 mW and a weak intensity state of about 0.5 mW. In the case where the signal output on the transmission side is about 0.5 mW corresponding to the weak intensity state, 2-1. As described above, there is little influence on the light emission state of the surface emitting semiconductor laser 502, and the light emission state does not change.

  Next, when the surface emitting semiconductor laser 501 is driven in a high intensity state of about 3 mW, light of about 0.3 mW is substantially incident on the surface emitting semiconductor laser 502. In this case, since the amount of light applied to the surface emitting semiconductor laser 502 is large, the light emitting state of the surface emitting semiconductor laser 502 is affected, the light emitting state of the surface emitting semiconductor laser 502 of the optical communication device 511 is changed, and the surface emitting semiconductor laser 502 is changed. The laser beam output of the light emitting semiconductor laser 502 is attenuated.

  When the amount of incident light is small, the light emission intensity of the surface-emitting type semiconductor laser 502 hardly changes and, for example, light of about 0.5 mW is output.

  When the amount of incident light is large, the light emission intensity of the surface emitting semiconductor laser 502 is greatly attenuated, and light attenuated to a light amount of, for example, about 0.1 mW is output.

  Therefore, this optical communication system functions as an inverter that outputs a “low” signal when the amount of incident light is large and outputs a “high” signal when the amount of incident light is small. 3A shows the time transition of the amount of light input to the surface emitting semiconductor laser 502, and FIG. 3C shows the time of the output current of the optical sensor 504 that has received the output of the surface emitting semiconductor laser 502. It is the graph which showed transition. As shown in FIG. 3, it can be seen that it is possible to transition from the both reception waiting state to the transmission / reception state.

  It should be noted that transition from the transmission / reception state to the both-reception standby state can be realized only by aborting transmission, and therefore the description is omitted.

2-3. Optical communication system for half duplex communication (Interrupt transmission / reception state and change to reception / transmission state)
Subsequently, the optical communication device 510 is set as the transmission side, the optical communication device 511 is set as the reception side, the optical communication device 511 interrupts the optical communication device 510, the optical communication device 510 is set as the reception side, and the optical communication device 511 is set as the transmission side. The operation for switching to will be described.

  First, 2-2. As shown in FIG. 5, the surface emitting semiconductor laser 501 of the optical communication device 510 on the transmission side is used for communication using a binary value of a light intensity in a strong state of about 3 mW and a light intensity in a weak state of about 0.5 mW. The surface-emitting type semiconductor laser 502 of the receiving side optical communication device 511 maintains a weak light intensity of about 0.5 mW in terms of direct current, and the signal from the transmitting side optical communication device 510 is transmitted. A signal is being received.

  In this state, an interrupt request for signal transmission from the receiving optical communication device 511 can be made by raising the output of the surface emitting semiconductor laser 502 of the receiving optical communication device 511 from 0.5 mW to 3 mW. The

  Hereinafter, the operation of the optical communication devices 510 and 511 when an interrupt signal is transmitted will be described. 1-5. As described above, when the output of the surface emitting semiconductor laser 502 of the optical communication device 511 on the receiving side is increased from 0.5 mW to 3 mW, the light output of the surface emitting semiconductor laser 501 is in a high intensity state of about 3 mW. Although there is not much fluctuation, the light output of the surface emitting semiconductor laser 501 decreases in a weak intensity state of about 0.5 mW, for example, about 0.1 mW. The light output fluctuation in the weak intensity state is 1-5. The optical communication device 510 senses that an interrupt request has been sent from the optical communication device 511.

  After sensing the interrupt request, the optical communication device 510 performs a process for stopping transmission, and after sending a transmission stop signal to the optical communication device 511, enters the reception state. Then, the optical communication device 511 that has received the transmission stop signal starts transmission of the optical signal.

  Thus, by using the optical communication system of the present invention, half-duplex communication can be realized using the single-wavelength surface emitting semiconductor lasers 501 and 502 and the single optical fiber 509.

  In the present embodiment, the driving current of the surface-emitting type semiconductor laser 101 and the output current from the optical sensor 102 are calculated by hardware using the circuit shown in FIG. The processing may be performed by software. In this case, when performing signal processing, for example, it is possible to take into account delay time and the like, and more complicated signal processing is possible.

  Below, the effect of Embodiment 2 is described.

  (1) By providing two optical communication devices 510 and 511 having the same configuration, an optical communication system capable of performing half-duplex communication having the characteristics described above is formed. Therefore, an optical communication system with excellent mass productivity can be obtained as compared with the case where an optical communication system is constructed using optical communication apparatuses each having a different structure.

  (2) Since the interruption is performed by raising the output of the surface emitting semiconductor laser 502 of the optical communication device 511 in the receiving state from 0.5 mW to 3 mW, a plurality of optical fibers, coaxial cables, semiconductor lasers having different wavelengths An interrupt can be performed without using the above.

1 is a cross-sectional view schematically showing an optical system of an optical communication device. The circuit diagram for performing the electrical process by an operational amplifier. The time transition figure of the current waveform which an optical sensor outputs. The time transition figure of the current waveform which an optical sensor outputs when intense light is irradiated. 1 is a schematic diagram showing an optical communication system obtained by using two optical communication apparatuses 200. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Optical block, 101 ... Surface emitting semiconductor laser as a semiconductor laser, 102 ... Optical sensor, 103 ... Stem, 104 ... Translucent plate, 105 ... Condensing lens, 106 ... Optical fiber, 107 ... Can package, 200 ... Optical communication apparatus 201 ... OP amplifier 202 ... inductor 203 ... capacitor 204 ... signal source 205 ... variable resistor 206 ... inductor 207 ... resistor 208 ... OP amplifier 209 ... capacitor 210 ... resistor DESCRIPTION OF SYMBOLS 211 ... Resistance, 212 ... Resistance, 501 ... Surface emitting semiconductor laser, 502 ... Surface emitting semiconductor laser, 503 ... Optical sensor, 504 ... Optical sensor, 505 ... Condensing lens, 506 ... Condensing lens, 507 ... Translucent Reference numeral 508, a transparent plate, 509, an optical fiber, 510, an optical communication device, and 511, an optical communication device.

Claims (4)

The local laser, the local optical sensor that receives a part of the light from the local laser, the signal is extracted from the local optical sensor, and the local laser is driven. An optical communication device of the local station provided with a drive circuit of the local station,
A semiconductor laser of another station optically coupled with the semiconductor laser of the local station, an optical sensor of another station that receives a part of light from the semiconductor laser of the other station, and a drive circuit of the other station, Having an optical communication device of another station having substantially the same configuration as the optical communication device of the local station,
(1) When receiving a signal from the optical communication device of the other station using the optical communication device of the own station,
The semiconductor laser of the other station transmits a modulation signal having a high frequency defined by a time constant shorter than a low frequency defined by a time constant of disturbance caused by temperature change and change with time received by the semiconductor laser of the local station. Driven to
The semiconductor laser of the local station is driven to maintain a weak laser emission state on a time average using the driving circuit of the local station,
When weak light is incident on the semiconductor laser of the local station from the semiconductor laser of the other station, the laser emission state of the local station is not affected, and when strong light is incident, Reflecting the intensity of the emission intensity of the other station in the intensity of the emission power of the semiconductor laser of the local station, using the phenomenon that the emission output of the semiconductor laser of the local station decreases due to disturbance of the laser emission state of the local station Let
When the emission intensity of the other station is weak, the emission output of the semiconductor laser of the own station is “weak”, and when the emission intensity of the other station is strong, the emission power of the own station is weaker than weak. The light output of the semiconductor laser is received by the local optical sensor,
Of the output of the optical sensor of the local station that receives a part of the emission output of the semiconductor laser of the local station, the low frequency component less than the frequency of the modulation signal transmitted from the other station is the semiconductor laser of the local station The driving power of the semiconductor laser of the local station is controlled so as to be removed as a disturbance component of the emission intensity of the laser, and a high frequency component equal to or higher than the frequency of the modulation signal transmitted from the other station is transmitted from the optical communication apparatus of the other station Output as
(2) When the optical communication device of the local station is used to interrupt the optical communication device of the other station while transmitting a signal from the optical communication device of the other station, the time average is weak. By switching from the reception state that is driven to maintain the laser emission state to the strong laser emission state, a “strong” signal is transmitted to the semiconductor laser of the other station, and the driving state of the semiconductor laser of the other station is strong or weak When the signal is in the “weak” state that occurs when the signal is in the “weak” state, and the optical sensor of the other station receives the “weak” light emission output, it is determined that an interrupt has occurred,
(3) When transmitting a signal to the optical communication apparatus of the other station using the optical communication apparatus of the own station, the local station and the other station of (1) are exchanged and executed.
(4) When interrupting the other station while transmitting a signal from the optical communication apparatus of the other station using the optical communication apparatus of the own station, the own station and the other of (2) An optical communication apparatus characterized in that the station is exchanged and executed.   The light intensity in the weak state is obtained by using a phenomenon in which the light emission state of the semiconductor laser is disturbed, which occurs when strong light is input from the another optical communication device. 2. The light according to claim 1, wherein when the light is input, the light emission intensity is set in a range lower than that in the weak state as compared with a case where strong light is not input from the another optical communication device. Communication device.   The optical communication apparatus according to claim 1, wherein the semiconductor laser is a surface emitting semiconductor laser. An optical communication system comprising two of the optical communication devices according to claim 1 and performing half-duplex communication.

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