JP2001053677A - Input level detecting method and optical transmission device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an input level detecting method which can measure the input level of a light signal without using any optical power meter and an optical transmission device which uses it. SOLUTION: The optical transmission device is equipped with a optic/electric converter 4 to which an optical signal as a transmission input is inputted within a limited input level and this method detects the input level of the optical signal to the optical/electric converter 4. An electric signal is generated by mixing the output of a data signal modulator 5 and the output of a signal generator 8 for light level detection, an electric signal generated through the optic/electric conversion of the converter 4 is branched and inputted to a signal demodulator 6 and an optical reception level detector 7 to demodulate the electric signal by the signal demodulator 6, and an optical reception level detector 7 which has correlation between the signal level of the generator 8 and the input level of the optical signal inputted to the converter 4 detect which of range-limited input levels (A1), (A2), or (A3) the input level of the optical signal to the converter 4 is.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical / electrical converter in an optical transmission apparatus for inputting an optical signal obtained by converting an electrical signal into electrical / optical data into an optical / electrical converter via an optical fiber cable and converting the signal into an electrical signal. The present invention relates to a method for detecting an input level of an optical signal, and particularly to an input level detecting method for detecting an input level of an optical signal without using a measuring device when the transmission distance is limited to a certain range, and using the input level detecting method. The present invention relates to an optical transmission device.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 7, an electric / optical converter 2 for converting an electric signal into an optical signal, an optical fiber cable 3 for transmitting an optical signal, and an input level of an optical signal transmitted and inputted. An optical transmission device including an optical / electrical converter 4 having a limited range is frequently used. In such an optical transmission device, the level of an optical signal transmitted from the optical transmitter to the optical receiver generally attenuates in accordance with the transmission distance (optical fiber loss). For example, as shown in FIG. Assuming that the signal level when output from the optical transmitter side is d1, the optical signal level when input to the optical receiver decreases as d2 and d3. For this reason, it is necessary to adjust the input level of the optical signal to the optical / electrical converter on the optical receiver side so that reception by the optical / electrical converter is always performed in the best state. When the length is short, the variable optical attenuator 10 is provided between the optical transmitter side and the optical receiver side, and the input level of the optical signal to the optical receiver is adjusted to the optimum level. Also, when using an optical transmission device in which the input level of the optical signal to the optical / electrical converter is limited to a certain range, the input level of the optical signal is measured by the optical power meter 10 and received at the best input level. The input level to the optical / electrical converter 4 was adjusted so as to be possible.

[0005] On the other hand, as shown in FIG. 5, an optical transmission device 1 having no optical power meter 10 has been used. In the optical transmission device 1, an electric signal frequency-modulated by the data signal modulator 5 is converted into an optical signal by the electric / optical converter 2, and an optical signal transmitted and input by the optical fiber cable 3 is converted by the optical / electric converter 4. And demodulates it into an original data signal by the signal demodulator 6 to output data. Further, the optical reception level detector 7 determines which input level of the optical signal is within the limited range, and adjusts the input level to the optical / electrical converter 4. As shown in FIG. 4, the optical reception level detector 7 includes a signal frequency band filter 7a, a frequency amplifier 7b, a detection circuit 7c, a DC voltage comparator 7d, and a determination output circuit 7e. The frequency bandpass filter 7a allows only the reception frequency to pass, the frequency amplifier 7b amplifies the data signal, converts the data signal to a DC voltage level by the detection circuit 7c, and the DC voltage comparator 7d artificially changes the input level of the optical signal. It is possible to determine which level is to be reached, and to indicate the input level by display or the like by the determination output circuit 7e.

[0004]

In the optical transmission apparatus 1 having the structure as shown in FIG. 5, the input level of the optical signal to the optical / electrical converter 4 is determined by changing the frequency by the band-pass filter 7a. Going along. However, as shown in FIG. 6, the levels d1, d2, and d3 of the data modulation signal are different when there is no data signal and when there is a data signal.
As shown in FIGS. 7A and 7B, the value constantly changes, and there is a problem that the measured value of the input level of the optical signal also changes. Further, even if the levels d1, d2, and d3 at the time of transmission of the optical signal are constant, if the level of the data modulation signal fluctuates, it is considered that the input level of the optical signal fluctuates. . For this reason, it was very difficult to set the input level of the optical signal to the optimum level and receive it.

Accordingly, an object of the present invention is to provide an optical transmission apparatus in which the input level of an optical signal to an optical / electrical converter is limited, if the level at the time of transmitting the optical signal is constant, the level of the data modulation signal fluctuates. Provided is an input level detection method capable of measuring an optical signal input level from a correlation with an electric signal level without using an optical power meter without regard to fluctuations of the optical signal input level, and an optical transmission device using the same. I do.

[0006]

According to a first aspect, an electric / optical converter 2 for converting an electric signal to an optical signal, an optical fiber cable 3 for transmitting an optical signal to the optical / electric converter 4, Light with a limited input level range of the input optical signal /
An optical converter for detecting an input level of an optical signal to the optical / electrical converter 4 in the optical transmission apparatus, the electrical signal including an output of a data signal modulator 5 and a signal for optical level detection. The output of the optical / electrical converter 4 is mixed with the output of the optical / electrical converter 4, and the electric signal obtained by the optical / electrical conversion is branched and input to the signal demodulator 6 and the optical reception level detector 7,
The electric signal is demodulated by the signal demodulator 6, and a correlation is previously established between the signal level of the optical level detection signal generator 8 and the input level of the optical signal input to the optical / electrical converter 4. The optical reception level detector 7 having
Thus, the input level of the optical signal to the optical / electrical converter 4 is detected among the input levels A1, A2, and A3 whose range is limited.

In the input level detection method according to the first aspect, the electrical / optical converter 2 is provided with the optical level detection signal generator 8 dedicated to optical reception level detection, and the optical / electrical converter 4 is provided.
The frequency detected by the optical signal level detector 7 provided on the side is converted to a DC voltage, and the input level of the optical signal is detected by the DC voltage comparator 7d from the correlation between the DC voltage and the input level of the optical signal. Can be displayed according to the input level.

According to a second aspect, the present invention provides a variable optical attenuator 9 between the electric / optical converter 2 and the optical / electric converter 4, and detects the optical input level by the optical input level detecting method according to claim 1. The optical transmission device is characterized in that the input level of the optical signal to the optical / electrical converter 4 is adjusted to an optimum level in accordance with the level. In the optical transmission device 1 according to the second aspect, the input level of the optical signal is detected according to the first aspect, and the input level of the optical signal is further adjusted by the optical variable attenuator 9 to the optimal level for the optical / electrical converter 4. Provided is an optical transmission device that can be set in the optical transmission device.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the drawings. Note that the present invention is not limited by this.

First Embodiment FIG. 1 is a simple block diagram showing an embodiment of an optical transmission device 1 used for explaining an input level detection method according to the present invention. The optical transmission device 1 includes a data signal modulator 5 for frequency-modulating an electric signal composed of a data signal such as an audio signal and an image signal, and a signal generator 8 for detecting an optical level (dedicated to the electric / optical converter 2). , An electrical / optical converter 2, an optical fiber cable 3, an optical / electrical converter 4, and a signal demodulator 6 for converting a frequency-modulated and transmitted optical signal back to an original electrical signal
And an optical reception level signal detector 7. This optical reception level signal detector 7 includes a frequency bandpass filter 7a, a frequency amplifier 7b, a detection circuit 7c,
It comprises a DC voltage comparator 7d and a judgment output circuit 7e.

Next, the optical transmission apparatus 1 configured as described above
The method of detecting the input level in the above will be described. First, the output signal of the data signal modulator 5 and the output signal of the signal generator 8 for optical level detection are mixed to form an electric data signal. The converted optical signal is output. Next, the optical signal is transmitted and input to the optical / electrical converter 4 through the optical fiber cable 3, the optical signal is optically / electrically converted, and the electric signal is output. The signal demodulator 6 demodulates the transmission signal and outputs an electric data signal. Further, in the optical reception level detector 7, only the signal corresponding to the frequency is passed by the band transmission filter 7a provided corresponding to the frequency of the optical level detection signal generator 8, and the corresponding signal is converted by the frequency amplifier 7b. Amplify further. Then, the signal is converted into a DC voltage level by the detection circuit 7c. Since the converted DC voltage has a correlation between the signal level of the optical level detection signal generator 8 and the input level of the optical signal in advance, the DC voltage is Comparator 7d
The input level of the optical signal is, for example, large level A1,
Which of the optimum level A2 and the small level A3 is detected. Then, the input level of the detected optical signal is, for example, a large level A by the determination output circuit 7e.
1. Lamps corresponding to the optimum level A2 and the small level A3 are displayed.

Second Embodiment FIG. 3 is a block diagram showing another embodiment of the optical transmission device 1 using the input level detection method according to the present invention.
The optical transmission device 1 according to the embodiment is further provided with an optical variable attenuator 9.
The input level of the optical signal to the optical / electrical converter 4 is detected at the optimum level A.
The configuration can be set to 2. Note that the basic operation and effect are the same as those described in the first embodiment, and thus detailed description is omitted here.

As described above, according to the input level detecting method of the present invention and the light transmitting apparatus using the same, the correlation between the signal levels A1, A2, and A3 of the electric signal and the signal level of the optical signal is determined in advance. Thus, without using the optical power meter 10, the transmitted optical signal can be optically / electrically converted, the input level of the optical signal can be detected in a pseudo manner, and the received level can be confirmed. To detect the signal level from the received signal, the signal frequency is tuned by a band-pass filter, but since the dedicated optical level detection signal generator 8 is mounted on the electrical / optical converter 2 side, the detection signal is detected. Does not change, and the measured value does not change. As a result, if the optical level of the optical level detection signal generator 8 to be transmitted is constant, even if the data signal is modulated and the signal level fluctuates, it is not considered that the optical signal level has fluctuated. The input level can be detected and received at the best level.

[0014]

According to the present invention, an optical receiving device is provided with a light level detecting signal generator corresponding to the optical receiving level detector on the optical / electrical converter side. Convert the frequency detected by the level detector to a DC voltage,
The input level of the received optical signal can be detected by the voltage comparator from the correlation between the DC voltage and the optical signal level of the optical level detection signal generator. In addition, an optical transmission device capable of adjusting the reception level of an optical signal to an optimum value according to the input level by using an optical variable attenuator can be obtained. The practical effect is large.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an optical transmission device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the level of a data signal on the transmitter side using the optical transmission device according to the first and second embodiments of the present invention. FIG. ) Indicates the time of modulation.

FIG. 3 is a block diagram illustrating a configuration of an optical transmission device according to a second embodiment of the present invention.

FIG. 4 is a block diagram illustrating a configuration of a reception level detector.

FIG. 5 is a block diagram showing a configuration of a conventional example of an optical transmission device.

FIGS. 6A and 6B are explanatory diagrams showing the level of a data signal on the transmitter side in a conventional optical transmission device, where FIG. 6A shows a non-modulated state and FIG. 6B shows a modulated state.

FIG. 7 is a block diagram showing another configuration of the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical transmission apparatus 2 Electric / optical converter 3 Optical fiber cable 4 Optical / electrical converter 5 Data signal modulator 6 Signal demodulator 7 Optical reception level detector 7a Frequency bandpass filter 7b Frequency amplifier 7c Detection circuit 7d DC voltage comparator 7e Judgment output circuit 8 Optical level detection signal generator 9 Optical variable attenuator 10 Optical power meter a1, a2, a3 Signal level of optical detection signal D1, D2, D3 Data signal level at the time of non-modulation d1, d2, d3 Data signal level during modulation

Claims (2)

[Claims] 1. An electric / optical converter 2 for converting an electric signal into an optical signal, an optical fiber cable 3 for transmitting an optical signal, and an optical / electrical converter having a limited input level range of an optical signal transmitted and input. And an optical signal input level to the optical / electrical converter 4 of the optical transmission apparatus 1 comprising the optical signal, wherein the electrical signal is an output of a data signal modulator 5 and a signal generator for optical level detection. 8 and the light /
The electric signal converted from light to electric by the electric converter 4 is branched and input to a signal demodulator 6 and an optical reception level detector 7, and the electric signal is demodulated by the signal demodulator 6.
The optical reception level detector 7 which has a correlation between the signal level of the optical level detection signal generator 8 and the input level of the optical signal input to the optical / electrical converter 4 in advance makes the optical / optical An input level detection method comprising detecting which of the input levels A1, A2, and A3 of the input level of the optical signal to the electrical converter 4 is limited. 2. A variable optical attenuator 9 is provided between the electrical / optical converter 2 and the optical / electrical converter 4, and the levels A1, A2, and A3 detected by the optical input level detection method according to claim 1.
An optical transmission apparatus characterized in that an input level of an optical signal to the optical / electrical converter 4 is adjusted to an optimum level corresponding to A3.