JP3061124B2 - Optical fiber transmission line measurement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication device connected via an optical fiber transmission line, and more particularly to an optical fiber transmission line measuring method for measuring a transmission delay time and a transmission distance.

[0002]

2. Description of the Related Art In recent years, in long-distance wired communication, optical communication using an optical fiber transmission line as a transmission line medium has been actively performed in order to increase the distance and speed.

[0003] Usually, as a method of measuring the transmission delay time in an optical fiber transmission line under such a situation, a method similar to that of other wired communication that does not use the optical fiber transmission line is used.

FIG. 5 is a diagram showing an example of a conventional transmission delay time measuring method. The transmission delay time measuring method in FIG. 5 is a measuring method in a transmission system in which the transmitting communication device 55 and the receiving communication device 56 have different reference clocks 51 and 52, respectively.

[0005] The transmitting side communication device 55 sets the time (transmission time: TA1) for transmitting a signal to the transmission path.
With reference to the reference clock 51 of FIG. Receiving communication device 5
6, the time at which the transmitted signal is received (reception time: T
B1) is recorded with reference to the receiving-side reference clock 52. The information of the transmission time (TA1) and the reception time (TB1) is collected at one point, and a transmission delay time (Tab) from transmission of a signal to reception of the signal is calculated. The transmission delay time is as shown in equation (1).

Tab = TB1−TA1 (1) FIG. 6 shows an example of another conventional transmission delay time measuring method.
In a transmission scheme similar to that shown in FIG. 5, a time (transmission time: T
A1) is recorded with reference to the transmission-side reference clock 61. The receiving-side communication device 65 transmits time information from the transmitting-side reference clock 61 to the receiving-side communication device 65 via a transmission path separately from the transmission data signal. If the transmission delay time of the time information is known, the reception-side reference time can be calculated by adding the transmission-side reference time and the transmission delay time of the time information. With reference to the receiving-side reference time, the time at which the signal transmitted from the transmitting side is received (receiving time: TB1) is recorded. The information of the transmission time (TA1) and the reception time (TB1) is collected at one point, and a transmission delay time (Tab) from transmission of a signal to reception of the signal is calculated. The transmission delay time is as shown in equation (2).

Tab = TB1−TA1 (2) FIG. 7 shows an example of another conventional transmission delay time measuring method.

A time (TA1) at which a signal is transmitted from the transmitting communication device 74 is recorded with reference to the transmitting reference clock 71. The signal transmitted from the transmission side communication device 74 is transmitted through the transmission path 7
6 and reaches the communication device 75 on the receiving side. The receiving side communication device 75 returns the received signal to the transmitting side and returns the transmitted signal as it is. The transmission-side communication device 74 receives the signal that has been sent back (reception time: T
A2) is recorded, and a round trip delay time (Tab + Tba) is calculated. When the same transmission path is used for going and returning, the transmission delay time (Tab) from the transmission side to the reception side can be assumed to be almost the same as the transmission delay time (Tba) from the reception side to the transmission side. One-way transmission delay time can be calculated. The transmission delay time is as shown in equation (3).

Tab ≒ Tba = (TA2−TA1) / 2 (3) In this method, when the delay time inside the communication device 75 on the receiving side is large, the time at which a signal is received from the communication device 75 on the receiving side ( TB1) and the time of transmission (TB2)
By transmitting this information to the transmitting side, it is possible to calculate a more accurate transmission delay time. The transmission delay time is as shown in equation (4).

Tab {Tba = {(TA2-TA1)-(TB2-TB1)} / 2 (4)

The problem in the transmission delay time measuring method shown in FIG. 5 is that the communication apparatuses on the transmitting side and the receiving side refer to different reference clocks, so that the transmission time and the receiving time are determined. If the reference time cannot be the same, for example, if one of the clocks is out of order, the difference between the two times will be an error, and if the transmitting communication device and the receiving communication device are at different points, It is also difficult to confirm the identity of the reference time.

To avoid this, it is effective to use a method as shown in FIG. 6 in which the transmitting side transmits the reference time to the receiving side so that the reference clock is the same. However, if the transmission delay time due to the transmission of the reference time information is not clear, there is still a problem that an error occurs in the relative reference time itself.

It is difficult to maintain the same time in each of the measuring methods described above, and it is difficult to verify the time. However, according to the measuring method shown in FIG. Since the measurement is performed by the reference clock, there is no problem of the identity of the reference time itself. However, in this measurement method, since one-half of the round-trip delay time is calculated as a one-way delay time, the delay time (Tab) from the communication device on the transmission side to the communication device on the reception side and the delay time from the reception device Delay time difference (Ta) of delay time (Tba) to reach the transmitting device
b-Tba), and a two-way communication from the transmission side to the reception side and from the reception side to the transmission side are required. Therefore, the measurement time is required until the delay time is measured and the error is corrected. There is a disadvantage that it requires.

(Object of the Invention) It is an object of the present invention to independently measure the transmission delay time in an optical fiber transmission line only on the receiving side.

Another object of the present invention is to measure the transmission delay time of an optical fiber transmission line with a simple system configuration by one-way communication.

Another object of the present invention is to measure a transmission delay time in an optical fiber transmission line without using a reference time synchronized with high accuracy between transmission and reception.

[0016]

According to the optical fiber transmission line measuring method of the present invention, a communication device on the transmitting side simultaneously transmits optical signals having different wavelengths from each other, and a communication device on the receiving side transmits two wavelengths of the received signal. Measuring a time difference between the optical signals, and calculating a transmission delay time or a transmission distance of the optical fiber transmission line based on the time difference and a refractive index of light of the optical fiber transmission line with respect to the two wavelength optical signals. And

In the method for measuring an optical fiber transmission line,
A communication device on the transmission side receives an electric signal for transmission as an input, and outputs an optical signal having different wavelengths from each other.
An optical coupler for transmitting the optical signals having the different wavelengths to one optical fiber transmission line; a communication device on the receiving side splitting the optical signal received from the optical fiber transmission line; A reference clock, a recording unit for recording respective reception times of optical signals of different wavelengths demultiplexed with reference to the reception reference clock, and an optical fiber transmission line for the recorded reception time and the optical signal of each wavelength. And a calculating unit for calculating the transmission delay time or the transmission distance of the optical fiber transmission line based on the refractive index of the light.

The optical signal to be transmitted can be transmitted as digital data in the form of a single pulse, a periodic pulse or a frame format, and the reception time is recorded by detecting the rising edge of the pulse or the beginning of the data frame format, respectively. Can be done. When transmitting digital data, the transmitting-side communication device transmits time information based on the transmitting-side reference clock, and the receiving-side communication device transmits the receiving-side reference clock based on the received time information and the transmission delay time. It is preferable to synchronize the time with the side reference clock.

More specifically, the communication device on the transmitting side comprises a first electric-optical converter for converting an electric signal for transmission into an optical signal having a first wavelength, and a second electric-optical converter for converting the electric signal into an optical signal having a second wavelength. A second electrical-optical converter for converting the optical signal into an optical signal;
And an optical coupler for transmitting the optical signal to one optical fiber transmission line. The communication device on the receiving side converts the optical signal received via the optical fiber transmission line into the first and second wavelengths. An optical demultiplexer for separating an optical signal into an optical signal, a first optical-to-electrical converter for converting the optical signal of the first wavelength into an electric signal, and a second optical-electrical converter for converting the optical signal of the second wavelength to an electric signal. 2 optical-to-electrical converter, a receiving-side reference clock, a first time recorder that records the reception time of the first electric signal with reference to the receiving-side reference clock, and a second time signal of the second electric signal. A second time recorder for recording the reception time, a refractive index data input unit for inputting refractive index information of light for the first and second wavelengths of the optical fiber transmission line, and the first and second times Based on the reception time recorded in the recorder and the refractive index information, the transmission time of the optical fiber transmission line or And a calculator for calculating the transmission distance.

(Effect) Optical signals of different wavelengths (λ1, λ2) are simultaneously transmitted from the transmission point to the optical fiber transmission line.
At the receiving point, the receiving time difference (Δt) of the optical signal is measured using only the reference clock at the receiving end, and based on the refractive index (n1, n2) for each wavelength, the light transmission speed (v1, v2).
, And further, the transmission speed (v1,
From the difference of v2), the transmission distance (S) of the optical fiber from the transmission point of the optical signal to the reception point and the delay time (t1, t2) of the optical signal of each wavelength are calculated.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] Next, a transmission delay time measuring method according to the present invention will be described with reference to FIGS. FIG. 1 is a diagram showing an embodiment of the present invention.

The transmission delay time measuring apparatus according to the present embodiment
It comprises a fiber transmission line 17 having a clear refractive index at each wavelength of an optical signal to be transmitted, and a transmission-side communication device 11 and a reception-side communication device 18 connected by the fiber transmission line 17.

The transmitting communication device 11 includes a signal output unit 12,
Branching unit 13, two E / 0 converters 1 for performing electric / optical conversion
4 and 15 and an optical coupler 16.

The signal output section 12 outputs a transmission signal. The time is defined as a transmission time T0, and this signal is
Branch in the direction. The split signals are the E / 0 converter 14 for the λ1 wavelength and the E / 0 converter 1 for the λ2 wavelength, respectively.
5 performs electrical-optical conversion, and respectively converts the wavelengths λ1, λ2
Are output. Each optical signal is subjected to wavelength multiplexing by the optical coupler 16 and transmitted to one optical fiber transmission line 17.

The receiving side communication device 18 includes an optical splitter 19 for splitting a received optical signal, and two O / Es for optical / electrical conversion.
It comprises converters 110 and 111, two reception time recording units 113 and 114 for recording reception time, an operation unit 115, and a refractive index data input unit 116.

Upon receiving the optical signal, the receiving side communication device 18 converts the optical signal received by the optical demultiplexer 19 into wavelengths λ1, λ
Into two optical signals. Each of the separated optical signals is converted into a 0 / E converter 110 for the λ1 wavelength and a 0 / E converter for the λ2 wavelength.
The optical-electrical conversion is performed by the E converter 111. The two converted electric signals are measured by the reception time recording units 113 and 114 with reference to the time of the reception-side reference clock 112,
The reception time T1 of the λ1 wavelength and the reception time T2 of the λ2 wavelength are obtained. The information on the reception time is calculated by the calculation unit 115 with the refractive index data n1 and n2 at each wavelength of the optical fiber transmission line previously input from the refractive index data input unit 116. The operation unit 115 calculates the λ1 wavelength reception time T1, λ2
Wavelength reception time T2, refractive index n at wavelengths λ1 and λ2
The transmission delay time and the transmission distance are calculated and output based on 1 and n2.

Hereinafter, a method of calculating the transmission delay time and the transmission distance in this embodiment will be described with reference to FIG.

FIG. 2 is a diagram showing the relationship among various data in the optical fiber transmission line 21. The transmission speeds v1 and v2 of the optical signals of two wavelengths λ1 and λ2 simultaneously transmitted from the transmission point in the optical fiber transmission line are uniquely determined by the respective refractive indices n1 and n2 in the optical fiber transmission line.
V1 = c / n1 and v2 = c / n2 (where c;
(Light speed of vacuum).

Also, between the communication devices connected via the optical fiber transmission line, the optical signals of two wavelengths transmitted from the transmission point at the same time T0 arrive at different times T1 and T2 at the reception point. From the difference Δt in the reception time and the transmission speeds v1 and v2 of each signal, it is possible to calculate the transmission delay times t1 and t2 of the signal at each wavelength from the transmission point of the optical signal to the reception point and the transmission distance S of the optical fiber. It is possible.

First, the transmission delay time difference Δ at the receiving point
At time t1, T2 or delay time t1, t2, Δt = T2-T1 = t2-t1 (5) The transmission distance S is as follows: S = v1 × t1 = v2 × t2 (6)

Next, the relationship between the refractive index and the speed is as follows: n1: n2 = v2: v1 (7), and the transmission speeds v1, v2 are: v1 = c / n1 (8) v2 = C / n2 (9) (However, c: speed of light in vacuum) Therefore, (5), (6), (7), (8), (9)
Therefore, the transmission delay time t1 of the wavelength λ1 and the transmission delay time t2 of the wavelength λ2 can be calculated as follows.

[0032]

(Equation 1) Further, the transmission distance S of the optical fiber transmission line 17 connecting the transmitting communication device 11 and the receiving communication device 18 can be calculated as follows.

[0033]

(Equation 2) Next, a specific transmission signal format of the present embodiment will be described with reference to FIG.

FIG. 3A is a time chart showing each system for measuring the transmission delay time using a single pulse signal or a periodic burst pulse signal.

In the transmission system shown in FIG. 3A, transmission data is output from the signal output unit 12 of the transmission-side communication device 11, and the time T1 when the reception data of the λ1 wavelength is received from the transmission time, and the transmission data of the λ2 wavelength Time T2 when received data was received
, The delay time difference Δt is obtained from this information and the refractive index information n
The transmission delay times t1 and t2 are calculated from 1 and n2.

FIG. 3B is a time chart showing a method for measuring a transmission delay time using a digital data signal having a frame format.

If the time interval from the first bit to the last bit of the frame format is longer than the transmission delay time difference (Δt) of the optical signal of two wavelengths, the transmission delay time can be measured.

Transmission data having a frame format is transmitted as transmission data, and a delay time difference Δt is obtained from a time T1 at which the reception data of the λ1 wavelength is received and a time T2 at which the reception data of the λ2 wavelength is received. The transmission delay times t1 and t2 are calculated from the rate information n1 and n2.

In the case of data transmission involving such a format, even if information for measuring the delay time is not multiplexed into the data portion or the format portion and transmitted, the head of the frame format of the λ1 wavelength optical signal is transmitted. Time (T1)
And the head time (T2) of the frame format of the optical signal of λ2 wavelength, a delay time difference is obtained,
The transmission delay time of the λ1 wavelength and the λ2 wavelength can be obtained.

[Second Embodiment] FIG. 4 is a diagram showing another embodiment of the present invention. This embodiment basically has the configuration shown in FIG. 1, and furthermore, the transmitting-side communication device includes a transmitting-side reference clock 42 and a multiplexing unit 44, and the receiving-side communication device includes a receiving-side reference clock 413. A time correction unit 416 is provided, and has a function of performing relative time synchronization between the transmission-side reference clock and the reception-side reference clock.

In the transmitting side communication device 41, the signal output unit 43
Then, a signal having a frame format as shown in FIG. 3 is output, and the multiplexing section 44 multiplexes and outputs the transmission-side reference time information from the transmission-side reference clock 42 for displaying the reference time of the transmission-side apparatus on the output. The multiplex output is two E / O
Λ1 and λ2 are converted by the converters 45 and 46 and the optical coupler 47.
The wavelength-multiplexed optical signal is converted to an optical fiber transmission line 48.
Send to

In the receiving side communication device 49, the optical demultiplexer 410
And two reception time recording units 414 and 415 via the O / E converters 411 and 412 to detect the arrival times of the λ1 and λ2 wavelength optical signals based on the reference time from the reception-side reference clock 413. λ1 wavelength reception time T
1. The transmission delay times t1 and t2 of the wavelengths λ1 and λ2 are calculated from the wavelength reception time T2.

Further, the arithmetic unit 417 separates and extracts the reference time information on the transmitting side multiplexed in the received optical signal,
The time when the transmitting communication device 41 transmits the optical signal is detected. The reception time correction unit 416 corrects the reception-side reference clock 413 by adding the transmission delay time to the transmission time information extracted by the calculation unit.

In this embodiment, it is possible to achieve relative time synchronization between the transmission-side reference clock and the reception-side reference clock.

In the above embodiment, an example is described in which a single optical fiber is used as the optical fiber transmission line between the transmitting side and the receiving side, but a plurality of optical fibers are used for the optical fiber transmission line. Alternatively, a configuration may be adopted in which optical signals of different wavelengths are transmitted from a transmitting-side communication device to a receiving-side device via different optical fibers to calculate a transmission delay time or a transmission distance. In addition, in the calculation of the transmission delay time or the transmission distance by the optical signals of a plurality of different wavelengths, an arithmetic method such as calculating an average value of the results calculated based on the reception times of the optical signal units of the two wavelengths is adopted. It can also be configured.

[0046]

According to the optical fiber transmission line measuring method of the present invention, it is possible to calculate the transmission delay time and the transmission distance of the optical fiber transmission line only from the information at the receiving end.

In addition, two-way communication is not necessarily required, and measurement can be performed only by one-way communication, so that calculation of delay time and transmission distance can be performed in a short time.

Further, since the delay time difference is usually smaller than the transmission delay time, when measuring the transmission delay time or the like in a transmission system that handles a data signal having a frame format, the delay time difference between the optical signals of the two wavelengths is different. Since the length of the frame format is shorter than the length of the normal frame format, it is possible to determine the delay time difference from the head of the frame format of the optical signal, and the frame format itself can be used as time information. That is, it is not necessary to multiplex time information as bit data even during data transmission, and it is possible to measure a delay time.
Therefore, the current communication information can be transmitted as it is without compressing the transmission information for measuring the transmission path.

Further, the present invention can be realized by using only one optical fiber transmission line. Even when the communication line is limited a little, the use of a spare core wire enables quick and simple operation. It is suitable for calculating approximate values of the transmission distance and the transmission delay time.

[0050]

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of a transmission delay time measuring method at a receiving end according to the present invention.

FIG. 2 is a conceptual diagram showing a transmission signal and a time relationship of an optical signal in an optical fiber transmission line.

FIG. 3 is a diagram showing types of transmission data and a time chart.

FIG. 4 is a diagram illustrating an embodiment of a transmission delay time measuring method at a receiving end according to the present invention.

FIG. 5 is a diagram showing an example of a conventional transmission delay time measuring method.

FIG. 6 is a diagram showing another example of a conventional transmission delay time measuring method.

FIG. 7 is a diagram showing still another example of the conventional transmission delay time measuring method.

[Explanation of symbols]

 11, 41 Transmission-side communication device 12, 43 Signal output unit 13 Branch unit 42 Transmission-side reference clock 14, 45 λ1 wavelength E / 0 converter 15, 46 λ2 wavelength E / 0 converter 16, 47 Optical coupler 17, 48 Optical fiber transmission line 18, 49 Receiving side communication device 19, 410 Optical demultiplexer 110, 411 λ1 wavelength 0 / E converter 111, 412 λ2 wavelength 0 / E converter 112, 413 Receiving side reference clock 113, 414 λ1 wavelength Reception time recording unit 114, 415 λ2 wavelength reception time recording unit 115, 417 calculation unit 116, 418 Refractive index data input unit 416 Time correction unit 117, 419 Delay time output 118, 420 Transmission distance output 21 Optical fiber transmission line 51, 52 , 61, 71 Reference clock 53, 62, 72 Transmission time record 54, 63, 73 Reception time record 55, 64, 74 Transmission side communication Communication device 56, 65, 75 Receiving communication device 57, 66, 76 Transmission path

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01M 11/00-11/02 H04B 10/08 H04B 17/00 G04F 10 / 04,10 / 06

Claims (6)

(57) [Claims] 1. An optical fiber transmission line measuring method for transmitting an optical signal between a communication device on a transmission side and a communication device on a reception side, wherein the communication device on the transmission side simultaneously transmits optical signals having different wavelengths from each other. the communication apparatus on the reception side, the optical fiber transmission line based on the refractive index of light the optical fiber transmission line for time difference measurements and the time difference between the two wavelengths of the optical signal between the two wavelengths of the optical signal received A transmission delay time or a transmission distance of the optical fiber. 2. A transmission-side communication device, comprising: an electro-optical conversion circuit that receives an electric signal as an input and outputs optical signals having different wavelengths; and an optical device that transmits the optical signal having the different wavelength to one optical fiber transmission line. A communication device on the receiving side having a coupler, a demultiplexer for demultiplexing the optical signal received from the optical fiber transmission line, a receiving-side reference clock, and a different demultiplexing device with reference to the receiving-side reference clock. A recording unit that records each reception time of the optical signal of the wavelength, and a transmission delay time of the optical fiber transmission line based on the recorded reception time and the refractive index of light of the optical fiber transmission line for the optical signal of each wavelength or 2. The optical fiber transmission line measuring method according to claim 1, further comprising an arithmetic unit for calculating a transmission distance. 3. The communication device on the transmission side transmits the optical signal to be transmitted as a single pulse or a periodic pulse, and the communication device on the reception side detects the timing of the step change of the pulse, thereby 3. The method according to claim 2, wherein the reception time is recorded. 4. A communication device on the transmitting side transmits an optical signal to be transmitted as digital data having a frame format, and a communication device on the receiving side detects the head of the frame format of the digital data to detect the reception time. 3. The method according to claim 2, wherein recording is performed. 5. The communication device on the transmission side multiplexes time information based on the reference clock on the transmission side into digital data and transmits the digital data. The communication device on the reception side receives the time information based on the received time information and the transmission delay time. 5. The optical fiber transmission line measuring method according to claim 4, wherein the time of the transmission side reference clock is adjusted to the time of the transmission side reference clock. 6. An optical fiber transmission line measuring method for transmitting an optical signal between a communication device on the transmission side and a communication device on the reception side, wherein the communication device on the transmission side transmits an electric signal for transmission to the first wavelength. A first electrical-optical converter for converting the optical signal into an optical signal, a second electrical-optical converter for converting the electrical signal into an optical signal of a second wavelength, and converting the first and second optical signals. An optical coupler for transmitting the signal to one optical transmission line, wherein the communication device on the receiving side separates the optical signal received via the optical fiber transmission line into optical signals of the first and second wavelengths. An optical demultiplexer, a first optical-electrical converter that converts the optical signal of the first wavelength into an electric signal, and a second optical-electrical converter that converts the optical signal of the second wavelength into an electric signal.
A first time recorder for recording the reception time of the first electric signal with reference to the optical-to-electrical converter, the reception-side reference clock, the reception-side reference clock, and the reception of the second electric signal A second time recorder for recording time, a refractive index data input unit for inputting refractive index information of light for first and second wavelengths of the optical fiber transmission line, and the first and second time recording An optical fiber transmission line measuring method, comprising: a calculation unit that calculates a transmission time or a transmission distance of an optical fiber transmission line based on a reception time recorded in a device and the refractive index information.