JP2000156664A - Optical communication equipment and optical transmitter- receiver utilizing it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical communication equipment and an optical transmitter- receiver where a dynamic range of an amplifier circuit of an optical receiver side is decreased by allowing an optical transmitter side of automatically adjust light intensity so as to reduce the power consumption and to facilitate the adjustment. SOLUTION: The optical communication equipment 10 includes an optical transmitter 12 that transmits an optical signal by means of a light emitting element 23, an optical receiver that receives the optical signal from the optical transmitter 12, and an optical fiber 11 that connects from the optical transmitter to the optical receive so as to transmit the optical signal. The optical transmitter includes a detection means 24 or the like that detects a reflected light from a transmitter side end 11a of the optical fiber and an end face of the receiver side of the optical fiber 11 and a control means 28 that controls drive of a drive circuit 22 of the light emitting element so that the light intensity at the receiver side end of the optical fiber reaches a prescribed level based on a reflected light detected by the detection means at the end of the optical fiber at the transmitter side and a delay time of the reflected light from the end of the receiver side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical communication device for performing communication by transmitting an optical signal through an optical fiber, and an optical transmitting and receiving device using the optical communication device.

[0002]

2. Description of the Related Art Conventionally, in the field of transmission of digital signals and the like, particularly for optical communication, a silica-based single mode optical fiber is used as an optical transmission line suitable for high-speed and large-capacity communication. And so on. And
In recent years, a multimode optical fiber such as a plastic optical fiber has been developed.
An application to digital communication over a relatively short distance, such as transmitting a signal at a transmission speed of about 1 / sec, has been performed.

[0003] Such a multimode optical fiber has a relatively large diameter, so that coupling with a light emitting element and a light receiving element or connection between optical fibers can be performed relatively easily. Utilization as a communication medium between them is being put to practical use. In optical communication between consumer digital devices, for example, in an optical fiber network which is an optical transmitting and receiving device, various lengths of optical fibers are prepared in advance as optical fibers for connecting the installation locations of the digital devices, and the communication distance is determined. Accordingly, an optical fiber having an appropriate length is selected and connected between an optical transmitter and an optical receiver via a connector, thereby forming an optical transmission line. Therefore, it is necessary that optical communication between digital devices can be performed without being affected by various lengths of optical fibers.

[0004]

However, an optical fiber generates an inherent optical transmission loss depending on the material and structure of the optical fiber. Therefore, the optical fiber reaches the optical receiver from the optical transmitter depending on the length of the optical fiber to be transmitted. The maximum intensity of the generated signal light will increase or decrease. As described above, since the maximum intensity of the signal light increases and decreases, the optical receiver side has a so-called dynamic range corresponding to a fluctuation range of the maximum photoelectric conversion voltage of the light receiving element which changes according to the length of the optical fiber used. It is necessary to prepare a sufficiently large amplifier circuit or a gain control circuit for amplifying the photoelectric conversion signal in accordance with the amplitude of the received light intensity.

Further, the adjustment of these amplification circuits and gain control circuits is performed by connecting an optical fiber having a desired length between an optical transmitter and an optical receiver in an optical fiber network or the like, and then adjusting the optical receiver side. It was necessary to make manual adjustments while monitoring the electrical signal that was photoelectrically converted in the above. Therefore, since the dynamic range of the amplifier circuit on the optical receiver side is large, there is a problem that power consumption is increased, component costs and assembly costs are increased, and adjustment work is troublesome.

In view of the above, the present invention reduces the dynamic range of the amplifier circuit on the optical receiver side by automatically adjusting the light intensity on the optical transmitter side, thereby reducing power consumption. It is an object of the present invention to provide an optical communication device and an optical transmission / reception device that facilitate adjustment work.

[0007]

According to the present invention, there is provided an optical transmitter for transmitting an optical signal by a light emitting element, an optical receiver for receiving an optical signal from the optical transmitter, and an optical transmitter. An optical fiber connected to guide an optical signal from the optical receiver to an optical receiver, the optical transmitter comprising: a transmitter-side end portion of the optical fiber and a receiver-side end surface. Detecting means for detecting the reflected light from the optical fiber, based on the delay time of the reflected light at the transmitter end and the reflected light from the receiver end detected by the detecting means, the receiver of the optical fiber Control means for controlling the drive circuit of the light emitting element so that the light intensity at the side end is at a predetermined level is attained by the optical communication apparatus.

According to the present invention, there is provided an optical transmitter for transmitting an optical signal by a light emitting element, an optical receiver for receiving an optical signal from the optical transmitter, and an optical signal from the optical transmitter. And an optical fiber connected to guide the optical receiver, comprising: an optical transceiver having an optical communication device,
Detecting means for detecting light reflected from the transmitter-side end and the receiver-side end of the optical fiber by the optical transmitter of the optical transmitting apparatus; and reflected light from the transmitter-side end detected by the detecting means. And control means for driving and controlling the drive circuit of the light emitting element such that the light intensity at the receiver side end of the optical fiber becomes a predetermined level, based on the delay time of the reflected light from the receiver side end. This is achieved by an optical transmitting / receiving device characterized by including:

According to the above configuration, before optical communication is performed, an optical signal is transmitted from the light emitting element of the optical transmitter to the optical fiber, and the optical signal of the optical signal is transmitted to the transmitter side of the optical fiber. The reflected lights respectively reflected at the end and the end on the receiver side are detected by the detecting means. The control means drives and controls the drive circuit of the light emitting element based on the delay time of the reflected light detected by the detection means, so that the light intensity from the light emitting element is adjusted, Then, the light intensity at the receiver-side end of the optical fiber is adjusted to a predetermined level via the optical fiber. Thus, the intensity of light entering the optical receiver from the end of the optical fiber on the receiver side is automatically adjusted to a predetermined level.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a preferred embodiment of the present invention will be described in detail with reference to FIGS. still,
Since the embodiments described below are preferred specific examples of the present invention, various technically preferred limitations are added.
The scope of the present invention is not limited to these embodiments unless otherwise specified in the following description.

FIG. 1 shows an embodiment of an optical transmission / reception apparatus using the optical communication apparatus of the present invention. For example, an optical transmission / reception apparatus for connecting a home called a connected home to an information provider in the world through a network. 1 shows a configuration example of a fiber network. House 200
Inside, various electric devices, information devices and the like are arranged. The house 200 is provided by an external content provider 201,
Home server 2 via access network 202
03, and information can be sent from the home server 203 to the content provider 201 via the access network 202. The house 200 is provided with an antenna 204, and the content provider 20
1 can be sent via artificial satellite 205. As a method of providing this information, in addition to a satellite link using the artificial satellite 205, a method using terrestrial waves can be adopted.

In the house 200 shown in FIG. 1, a control system 210 for the above-described devices and a multimedia system 220 are provided. The control system 210 includes devices used in ordinary households, for example, an electric light 210A, a refrigerator 210B, a microwave oven 210C,
Air conditioner 210D, electric carpet 210
E, a signal path for controlling the gas water heater 210F, the home medical device 210G, and the like are formed. On the other hand, the multimedia system 220 includes devices corresponding to the multimedia age, such as a computer 220A, a telephone 220B, an audio device 220C, a portable information device 220D, a digital still camera 220E, a printer / facsimile 220F, and a digital video camera 220.
G, a game machine 220H, a DVD (digital versatile disc or digital video disc: trademark) player 220I, a signal path for controlling the television receiver 220J, and the like. Various devices of the control system 210 and the multimedia system 220 include:
It is sequentially connected to the home server 203 in a ring shape using an optical fiber described later, and transmits and receives an optical signal by a one-core unidirectional optical communication system, thereby controlling on / off control of each device of the control system 210 and various devices. And information such as turning on and off a switch of a television receiver 220J of the multimedia system 220, and supplying and sending information.

FIG. 2 shows an embodiment of an optical communication apparatus for connecting the home server 203 between various devices of the control system 210 or the multimedia system 220 shown in FIG. In FIG. 2, the optical communication device 10 includes:
Optical transmission is performed by a so-called one-core unidirectional optical communication system, and an optical fiber 1 is transmitted from one device M1 to another device M2.
1 for optical transmission. The optical communication device 10 includes an optical transmitter 12 connected to one device M1.
And an optical receiver 13 connected to the other device M2, and an optical fiber 11 for optically connecting the optical transmitter 12 and the optical receiver 13. Here, the optical receiver 13 includes: a photoelectric conversion element that receives an optical signal transmitted through the optical fiber 11 and converts the optical signal into an electric signal; and an amplification circuit that amplifies an output signal from the photoelectric conversion element. It is configured to output an electric signal corresponding to the optical signal. The devices M1 and M2 are the devices in the control system 210, the devices in the multimedia system 220, the home server 203, and the like shown in FIG.

Here, the optical transmitter 12 in the optical communication device 10 is configured in more detail as shown in FIG. In FIG. 3, the optical transmitter 12 first has a digital signal generation source 21, a drive circuit 22, and a light emitting element 23. Further, it also has an optical system 24 as a detecting means, a half mirror 25, a photoelectric conversion element 26, and an amplifier circuit 27. This half mirror 25 is provided as a light separating means between the light emitting element 23 and the optical system 24,
The photoelectric conversion element 26 on which the reflected light reflected by the half mirror 25 is incident, and the amplification circuit 27 for amplifying an output signal of the photoelectric conversion element 26 are provided.
Further, there is provided an output control section 28 which is a control means for controlling the drive of the drive circuit 22 based on the signal from the amplifier circuit 27.

The digital signal source 21 outputs a digital signal based on the output signal of the device M1. The drive circuit 22 outputs a drive signal for driving the light emitting element 23 based on a digital signal from the digital signal source 21. The light emitting element 23 is, for example, a semiconductor laser element that emits a laser beam having a wavelength of about 650 nm, and emits light according to a drive signal from the drive circuit 22. The optical system 24 is, for example, a convex lens, and focuses an optical signal emitted from the light emitting element 23 on the transmitter-side end surface 11a of the optical fiber 11, which is the transmitter-side end. The optical fiber 11 is, for example, a general PMMA.
(Polymethyl methacrylate) SI (Step In
A dex) type POF is used, and its length is, for example, about 20 m, and both end faces are formed as mirror-like smooth polished surfaces in order to prevent scattering of signal light.

The half mirror 25 transmits an optical signal from the light emitting element 23 and transmits the optical fiber cable 1.
The light reflected from the end face 11a on the transmitter side and the end face 11b (see FIG. 2) on the receiver side, which is the end on the receiver side, are separated from each other. The photoelectric conversion element 26 converts the optical signal of the reflected light into an electric signal when the reflected light separated by the half mirror 25 enters. The amplification circuit 27 amplifies the electric signal from the photoelectric conversion element 26 and outputs the electric signal to the output control unit 28.

Here, the light emitting element 23 is set to have a half width of about 1 ns,
When driven at a peak intensity of about 1 mW to emit a single pulse light, the return light is the first pulse reflected by the end face 11a of the optical fiber 11 on the transmitter side as shown in the graph of FIG. Wave A and receiver end face 11b of optical fiber 11
Is detected as the second pulse wave B reflected by the. The first pulse wave A has a peak intensity of about 300 μW,
The second pulse wave B has a peak intensity of about 18 μW,
The time difference (delay time) was about 100 ns. Generally, the fiber length is D (m), the delay time is T (second), the refractive index of the optical fiber is n, and the light speed is c (3 × 10 ⁸ m / sec).
And the fiber length D is

D = T × c / 2n Equation 1

In the case of a PMMA optical fiber, since n = 1.49, D ≒ 20.1 (m) is calculated. Thus, the length of the optical fiber can be automatically measured from the delay time of the return light by the optical fiber.

In order to perform such an operation, the output control unit 28 includes a programmable controller 28a, a timer counter 28b, and an output constant table 28, as shown in FIG.
c.

This programmable controller 28a
Measures the time difference (delay time) between the first pulsed light A and the second pulsed light B due to the electric signal input from the amplifier circuit 27. When the first pulsed light A is detected, the timer counter 28b is activated, and when the second pulsed light B is detected, the timer counter 28b is stopped. Measured. Here, the timer counter 28b has, for example, about 246 MHz.
(The clock cycle ω is about 4 × 10 ⁻⁹ seconds). Thus, if the delay time T (second) is the clock cycle ω (10 ⁻⁹ second),

T = count value × ω (2)

Is given by

In a PMMA optical fiber, an optical signal having a wavelength of 650 nm is approximately 0.14 d.
A transmission loss (fiber loss coefficient Cf) of B / m occurs.
Therefore, the fiber transmission loss Lf (dB) is

Lf = D × Cf Equation 3

Is given by Thereby, the optical fiber 1
1 is represented by L (T
x) (dB), assuming that the coupling loss at the end face 11b on the receiver side is L (Rx) (dB), the total transmission loss Lt (d
B)

Lt = Lf + L (Tx) + L (Rx) Equation 4

Given by Therefore, a predetermined level (for example, -10 dBm) in the photoelectric conversion element of the optical receiver 13
In order to obtain the light intensity Pd, the light output intensity Ps (dBm) of the light emitting element 23 is

Ps = Lt−Pd Equation 5

Must be adjusted to the value given by

As a result, the transmission loss Lf at the length of about 20.1 m of the optical fiber 11 calculated as described above is obtained.
Is calculated to be about 2.8 dB from Equation 3, and in the above configuration, the coupling loss L (Tx) between the light emitting element 23 and the end face 11 a of the optical fiber 11 on the transmitter side is about 1.8 dB.
B, the coupling loss L (Rx) between the end face 11b of the optical fiber 11 on the receiver side and the photoelectric conversion element of the optical receiver 13 is:
About 21. dB. Therefore, these coupling losses L (T
x), L (Rx) and the fiber transmission loss Lf of the optical fiber 11 calculated as described above, the total coupling loss Lt
Is calculated from the above equation (4). Further, the intensity Pd of the optical signal incident on the photoelectric conversion element of the optical receiver 13 is about 100 μm.
The drive circuit 22 is driven and controlled by Expression 5 so that the light output intensity of the light emitting element 23 becomes Ps so that W (approximately −10 dB in dB notation).

Here, the programmable controller 28a of FIG. 3 does not perform the above operation every time.
A timer counter value-light emission output correspondence table (see FIG. 5) indicating the light emission output intensity Ps corresponding to the timer counter value is registered in the output constant table 28c, and the output constant table corresponds to the count value of the timer counter 28b. The emission output intensity Ps is obtained by reading the emission output intensity from the timer counter value-emission output correspondence table registered in 28c. The programmable controller 28a
Means that the count value of the timer counter 28b is, for example, 125
Is exceeded, that is, if the standby time of the reflected signal exceeds 500 ns, the control operation is stopped assuming that the effective length of the optical fiber 11 is out of the specified range.

Optical communication device 10 according to an embodiment of the present invention
Is configured as described above, and operates as follows based on the flowcharts shown in FIGS. First, in FIG. 6, when the power of the optical communication device 10 is turned on, first, in step ST1, the output control unit 28 operates to emit light of the optical transmitter 12 corresponding to the length of the optical fiber 11. The output of the element 23 is adjusted. Then, in step ST2, the termination status is set to TRU as described later.
In the case of E, optical communication is started in step ST3, and when the optical communication is completed, the operation ends. Also,
If the end status is FALSE in step ST2, an error is displayed in step ST4.
The operation will be stopped.

Here, the output adjustment of the output control unit 28 in step ST1 is performed in more detail according to the flowchart shown in FIG. In FIG. 7, first,
At step ST11, the programmable controller 2
8a resets the count value of the timer counter 28b, sends a single pulse as a control signal to the drive circuit 22 in step ST12, and causes the light emitting element 23 to emit a pulse. Then, the programmable controller 28a
When a signal corresponding to the first pulsed light A is input from the amplifier circuit 27, the count operation of the timer counter 28b starts, and in step ST13, the timer counter 28a
Read the count value from. Then, in step ST14, when a signal corresponding to the second pulse light B is input, the programmable controller 28a determines that return light has been detected, stops the timer counter 28b, and sets the timer counter 28b based on the count value at that time. In step ST15, the timer count value registered in the output constant table 28c-
The light emission output intensity is read from the light emission output correspondence table. Then, the programmable controller 28a performs step S
At T16, a control signal corresponding to the emission output intensity is output to the drive circuit 22, and an output control voltage value of the drive circuit 22 is set. Here, the programmable controller 2
8a sets the end status to TR in step ST17.
Set to UE and end the operation. Thereafter, as described above, optical communication is started in step ST3 (see FIG. 6), and when the optical communication is completed, the operation ends.

By the way, as shown in FIG.
If the signal corresponding to the second pulsed light B is not input at 14, the programmable controller 28a returns to step ST13 until the count value of the timer counter 28b reaches a predetermined number (for example, 125) at step ST18. The reading of the count value of the timer counter 28a is repeated. However, in step ST18, when the count value exceeds the predetermined number, the length of the optical fiber is out of the specified range (for example, the optical fiber 11 is not connected or the optical fiber 11 is too long, and the return light is not detected. For example, the timeout is set. Then, in step ST19, the end status is set to FALSE, and the operation is stopped. Thereafter, as described above, an error is displayed in step ST4 (see FIG. 6), and the operation is stopped.

Thus, when the power is turned on, the light emitting element 23 of the optical transmitter 12 corresponding to the length of the optical fiber 11 is turned on.
The light emission output intensity of the optical fiber 1 is adjusted.
When the length of the optical receiver 13 is about 5 m and about 30 m, the optical receiver 13
The light intensity of the incident light on the photoelectric conversion element of
2 μW, about 96 μW. Thus, the fluctuation of the maximum light intensity on the optical receiver 13 side is at most ± 10
μW, and even if the length of the optical fiber 11 is changed,
The allowable width of the optical receiver 13 for signal fluctuation, that is, the so-called dynamic range, is about 0.9 dB. In this case, since the light-to-current conversion efficiency of the photoelectric conversion element used in the light receiver 13 is about 40%, the output of the light receiver 13 by a current-voltage conversion amplifier having an impedance value of about 10 kΩ, a so-called transimpedance amplifier. The voltage is about 450 mV and about 380 mV, for example, when a 5 m optical fiber or a 30 m optical fiber is used.
Since the output voltage does not fluctuate greatly, the power source of the transimpedance amplifier is only 1.5
It is sufficient to supply a voltage of about V.

On the other hand, in the case of the conventional optical communication device, the dynamic range of the optical receiver is about 30 m.
, Which is the difference between the transmission loss caused by the optical fiber of 5 m and 5 m.
5 dB is required. Therefore, when the light intensity of the light emitting element cannot be adjusted according to the length of the optical fiber, it is necessary to maintain a constant light intensity, for example, to reduce the light intensity to 1 mW.
, The output voltage at the optical receiver 13 reaches about 1.4V. For this reason, in order to prevent the signal waveform of the output voltage from being distorted, it is necessary to supply a power supply voltage of about 5 V as a power supply of the transimpedance amplifier. Thus, when optical fibers of various lengths are used, a wide dynamic range is required for the amplifier of the optical receiver to correspond to the length of the optical fiber. It had to be set high enough.

As described above, according to the optical communication device 10 according to the embodiment of the present invention, the emission output intensity of the light emitting element of the optical transmitter is adjusted according to the length of the optical fiber 11. The optical signal of a predetermined level always enters the optical receiver 13. Then, even if there is a difference in transmission loss depending on the length of the optical fiber 11 when the optical fiber 11 having a different length is used, the intensity of the transmission optical signal in the optical transmitter 12 does not vary. Therefore, in the optical transmitter 12, the dynamic range of the amplifier circuit 27 is significantly reduced, and the power supply voltage can be significantly reduced. Further, since the gain control circuit for the photoelectric conversion signal is not required on the receiver 13 side, the power consumption is reduced and the cost is reduced.

Further, according to the optical fiber network according to the embodiment of the present invention, when performing optical communication, the drive circuit 22 for the light emitting element 23 of the optical transmitter 12 corresponds to the length of the connected optical fiber 11. Is adjusted,
The light intensity of the optical signal on the receiving end surface 11b of the optical fiber 11 is set to a predetermined level adjusted by the output control unit 28 in advance. The optical signal emitted from the end face 11 a of the optical fiber 11 on the receiver side is transmitted to the optical receiver 1.
3, and is converted into an electric signal by a photoelectric conversion element, further amplified by an amplifier circuit, and becomes an electric signal of a predetermined level. Thus, from the optical transmitter 12 to the optical receiver 1
The optical communication of the signal to 3 is performed. Therefore, even when the optical fibers 11 having different lengths are selected and connected, the optical signal at the optical receiver 13 is always automatically adjusted to a constant level.
Is not affected by the transmission loss due to the length. Therefore, an optical fiber network that can reduce power consumption and cost can be configured.

In the above embodiment, the output control of the light emitting element corresponding to the length of the optical fiber of the optical communication device is automatically performed when the power of the optical communication device, especially the optical transmitter is turned on. However, the present invention is not limited to this. For example, it may be performed immediately before an optical signal is transmitted by optical communication, or may be performed periodically or manually when desired by the user. It is clear. Further, in the above-described embodiment, the optical communication device 10 used for the home optical fiber network has been described. However, the present invention is not limited to this, and may be applied to an optical fiber network such as a so-called SOHO or an optical fiber network in a company or a region. The present invention can also be applied to this.

[0041]

As described above, according to the present invention, by automatically adjusting the light intensity on the optical transmitter side, the dynamic range of the amplifier circuit on the optical receiver side is reduced, and the power consumption is reduced. It is possible to provide an optical communication device and an optical transmission / reception device in which the adjustment work is reduced and the adjustment work is facilitated.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration example of an optical fiber network including a control system and a multimedia system including an optical communication device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an embodiment of an optical communication device for connecting each device in the optical fiber network of FIG. 1;

FIG. 3 is a block diagram showing a configuration of an optical transmitter in the optical communication device of FIG.

FIG. 4 is a graph showing an output signal of a photoelectric conversion element in the optical transmitter of FIG.

FIG. 5 is a table showing an example of a timer count value-light emission output correspondence table registered in an output constant table in the optical transmitter in FIG. 3;

FIG. 6 is a flowchart illustrating an operation of the optical transmitter in FIG. 3;

FIG. 7 is a flowchart illustrating an operation of an optical control unit in the optical transmitter in FIG. 3;

[Explanation of symbols]

10: Optical communication device, 11: Optical fiber, 12
..Optical transmitter, 13 optical receiver, 21 digital signal source, 22 driving circuit, 23 light emitting element,
Reference numeral 24: optical system, 25: half mirror (light separating means), 26: photoelectric conversion element, 27: amplifier, 2
8 ... output control unit, 28a ... programmable controller, 28b ... timer counter, 28c ...
Output constant table.

Claims (6)

[Claims] An optical transmitter for transmitting an optical signal by a light emitting element, an optical receiver for receiving an optical signal from the optical transmitter, and an optical transmitter connected to guide the optical signal from the optical transmitter to the optical receiver. An optical communication device, comprising: an optical fiber, wherein the optical transmitter detects reflected light from a transmitter-side end portion and a receiver-side end surface of the optical fiber; Based on the delay times of the reflected light from the transmitter end and the reflected light from the receiver end detected by the above, the light intensity at the receiver end of the optical fiber is set to a predetermined level. An optical communication device, comprising: control means for driving and controlling a light emitting element driving circuit. 2. The detecting means is disposed between the light emitting element and a transmitter-side end of the optical fiber, and the transmitter-side end of the optical fiber and the receiver-side end of the optical fiber. The light according to claim 1, further comprising: a light separating unit that separates reflected light from the first and second light sources; and a photoelectric conversion element that converts return light separated by the light separating unit into an electric signal. Communication device. 3. The control means processes an output signal of a photoelectric conversion element, and calculates a delay time of return light from a transmitter side and a receiver side end of the optical fiber due to pulse emission of the light emitting element. 2. The optical communication device according to claim 1, wherein the length of the optical fiber is calculated based on the calculated value, and a control signal is output in response to a transmission loss caused by the length of the optical fiber. 4. The apparatus according to claim 3, wherein said control means outputs a control signal based on a previously registered delay time and an output correspondence table of the light emission intensity of said light emitting element. Optical communication device. 5. The optical communication device according to claim 1, wherein drive control of the drive circuit by the control circuit is performed prior to optical communication. 6. An optical transmitter for transmitting an optical signal by a light emitting element, an optical receiver for receiving an optical signal from the optical transmitter, and an optical receiver connected to guide the optical signal from the optical transmitter to the optical receiver. An optical transmitter / receiver having an optical communication device, comprising: an optical fiber, wherein the optical transmitter of the optical transmission device transmits reflected light from a transmitter-side end portion and a receiver-side end surface of the optical fiber. Detecting means for detecting, based on the delay time of the reflected light at the transmitter end and the reflected light from the receiver end detected by the detecting means, the light at the receiver end of the optical fiber Control means for controlling the driving circuit of the light emitting element so that the intensity becomes a predetermined level.