JP4352810B2 - Insertion loss measurement method for multiplexer / demultiplexer - Google Patents

Description

  The present invention relates to a method of measuring insertion loss of a multiplexer / demultiplexer, and in particular, a multiplexer capable of easily measuring the insertion loss of a multiplexer or a duplexer having a plurality of channels for each channel. -It relates to a method for measuring the insertion loss of a duplexer.

  In an optical transmission system, wavelength division multiplexing (WDM) for transmitting a plurality of optical signals having different wavelengths through one optical fiber is used, and effective use of one optical fiber is achieved. . In an optical transmission system, an optical signal is added in the middle of a transmission system, or light of a specified wavelength is extracted. An optical component (optical device) for this purpose is a wavelength multiplexer or optical multiplexer. A demultiplexer (OMUX, hereinafter referred to as a multiplexer), a wavelength demultiplexer or an optical demultiplexer (ODMUX, hereinafter referred to as a demultiplexer). The multiplexer introduces light of n wavelengths of wavelengths λ1, λ2,..., Λn into one optical fiber, and the demultiplexer receives the multiplexed signal input from one optical fiber as wavelength λ1. , Λ2,..., Λn are separated into optical signals having respective wavelengths.

  It is important for the normal operation of the system to understand whether the multiplexer and demultiplexer incorporated in optical transmission are operating normally and whether deterioration or abnormality has occurred due to secular change. is there. Therefore, the multiplexer and the duplexer are checked at the time of construction, when an abnormality occurs, and periodically or as necessary. This check can be performed by measuring the insertion loss of the multiplexer or duplexer.

  Conventionally, a power meter (PM) is used to measure the insertion loss of a multiplexer or duplexer. The power meter has functions such as converting input light into an electrical signal by a photodiode, measuring the photocurrent, calculating optical power, and displaying it on a display. A typical example of this is gain measurement. By measuring the input power and output power of a multiplexer or demultiplexer with a power meter and subtracting the output value from the input value, the multiplexer or demultiplexer is used. You can know the loss.

  FIG. 3 shows a configuration example for realizing a conventional insertion loss measurement method in a multiplexer. A tunable laser source (TLS) 11 is used as a measurement light source, and a coupler 12 is connected to the tunable light source 11 via an optical fiber 31. A power meter 13 (PM1) is connected to one of the branch outputs of the coupler 12 via an optical fiber 34, and an optical fiber 32 is connected to the other of the branch outputs. One of the plurality of input terminals of the multiplexer 14 is connected to the optical fiber 32. A power meter 15 (PM2) is connected to the output terminal of the multiplexer 14 through an optical fiber 33. The variable wavelength light source 11 has a built-in diffraction grating, and the wavelength of the output light can be freely changed by rotating the diffraction grating.

  A plurality of input terminals of the multiplexer 14 correspond to different wavelengths such as wavelengths λ1, λ2,..., Λ (n−1), λn (channels ch1 to chn) from the top to the bottom of FIG. First, the optical fiber 32 is connected to the input terminal (ch1) having the wavelength λ1. In this state, light of wavelength λ1 is generated from the wavelength tunable light source 11, and the optical power is measured by the power meters 13 and 15. By subtracting the measured value S2 from the power meter 15 from the measured value S1 from the power meter 13 (S1-S2), the insertion loss of the multiplexer 14 at ch1 (wavelength λ1) can be calculated.

  Similarly, the wavelength of the light output from the wavelength tunable light source 11 is changed to λ2, λ3,... And the optical fiber 32 is connected to the next input terminal of the multiplexer 14, while the power meter 13 is switched. , 15 are sequentially executed, and the insertion loss is calculated based on the measured value.

  FIG. 4 shows a configuration example for realizing a conventional insertion loss measuring method in the duplexer. When measuring the insertion loss of the duplexer, the duplexer 16 is disposed between the optical fibers 32 and 33. The duplexer 16 includes a plurality of output terminals corresponding to wavelengths λ1, λ2,..., Λn (ch1 to chn). While changing the wavelength of light output from the wavelength tunable light source 11 to λ1, λ2,..., One of the output terminals of the duplexer 16 is selected according to the wavelength, and the power meters 13 and 15 are selected. To measure the optical power. For example, when light of wavelength λ1 is generated from the wavelength tunable light source 11, the optical power at the output terminal corresponding to the wavelength λ1 of the duplexer 16 is measured by the power meter 15, and the measured value S1 of the power meter 13 and the power meter are measured. The difference (S1−S2) from the 15 measured values S2 is calculated as the insertion loss of the duplexer 16 at ch1 (wavelength λ1).

  FIG. 5 shows another configuration example for realizing the conventional insertion loss measuring method in the duplexer. In the measurement method of FIG. 3, it is necessary to change the connection of the input terminals of the optical fiber 32 and the multiplexer 14 by the number of input terminals. Similarly, in the measurement method of FIG. 4, it is necessary to change the connection between the plurality of output terminals of the duplexer 16 and the optical fiber 33 by the number of output terminals. FIG. 5 eliminates this inconvenience, and the connection can be changed simply by switching the optical switch 17 in accordance with the wavelength change of the output light of the wavelength tunable light source 11.

  A coupler 12 is connected to the variable wavelength light source 11 via an optical fiber 31. The power meter 13 (PM1) is connected to one of the branch outputs of the coupler 12 via the optical fiber 34, and the optical fiber 32 is connected to the other. An input terminal of the optical switch 17 is connected to the optical fiber 32. The optical switch 17 includes a plurality of output terminals corresponding to one input terminal and the number of input terminals of the multiplexer 14. The plurality of output terminals of the optical switch 17 and the plurality of input terminals of the multiplexer 14 are connected in a one-to-one relationship. A power meter 15 (PM2) is connected to the output terminal of the multiplexer 14 through an optical fiber 33.

  When the wavelength of the light output from the wavelength variable light source 11 is λ1, the optical switch 17 selects the input terminal of the multiplexer 14 corresponding to λ1. This state is the same as in FIG. Here, the optical power is measured by the power meters 13 and 15, and the insertion loss of the multiplexer 14 at λ1 is calculated. Thereafter, λ2, λ3,... Λn and the output light of the wavelength tunable light source 11 are changed, and the optical switch 17 is sequentially switched accordingly, and the optical power is measured by the power meters 13 and 15 each time. Thus, the insertion loss of the wavelength λ2 to λn of the multiplexer 14 is calculated.

  In FIG. 5, a combination of the duplexer 16 and the optical switch 17 may be used instead of the combination of the optical switch 17 and the multiplexer 14. In this case, the duplexer 16 is installed at the front stage as shown in FIG. 4, and the optical switch 17 is installed at the rear stage.

  An optical loss monitoring device that measures optical power and monitors fluctuations in optical loss of optical components and optical lines has been proposed (see, for example, Patent Document 1). An object to be measured is connected to the first branch point of the branch part connected to the light source via a reflective point having transparency, and the first optical power measuring instrument is connected to the second branch point of the branch part. The third branching point of the branching unit is connected to a second optical power measuring device for measuring the reflected light from the reflecting point, and the third optical power measuring device is connected to the object to be measured. Based on the optical power values P1, P2, and P3 by the first, second, and third optical power measuring devices, the optical loss of each of the light source, branching portion, reflection point, and object to be measured is measured. When a predetermined reference value is exceeded, an alarm is issued and a display is made. By grasping the optical loss of each part, it becomes possible to specify the factor of fluctuation of the optical loss.

Japanese Patent Laid-Open No. 11-271178 (FIG. 1)

  However, according to the conventional method for measuring the insertion loss of a multiplexer / demultiplexer, when the configuration of FIGS. 3 and 4 is used, the measuring device and the light on the multi-wavelength side are changed every time the measurement channel on the multi-wavelength side is changed. It is necessary to change the connection with the fiber. Further, when the configuration of FIG. 5 is used, there is a problem that the measurement accuracy does not increase because the loss reproducibility of the optical switch itself is poor.

  Further, even if Patent Document 1 is used to measure the loss of a wavelength multiplexer or wavelength demultiplexer, it cannot be applied to a wavelength multiplexer or wavelength demultiplexer that handles wavelength multiplexing because the light source is not variable in wavelength. In addition to the need to install reflection points, the optical power measuring instrument is installed in three locations, and the measurement work is complicated.

  Accordingly, an object of the present invention is to provide a multiplexer / demultiplexer that can easily measure the insertion loss in each channel of the multiplexer / demultiplexer without changing the connection on the multi-wavelength side to be measured. An object of the present invention is to provide a method for measuring insertion loss of a device.

  In order to achieve the above object, the present invention measures the insertion loss of a multiplexer that multiplexes a plurality of optical signals with different wavelengths, or a demultiplexer that demultiplexes a wavelength-multiplexed optical signal for each wavelength. In the insertion loss measurement method of the multiplexer / demultiplexer, the insertion loss of each channel of the reference demultiplexer or multiplexer used only at the time of measurement is obtained, and the same channels on the multi-wavelength side are mutually connected. In this state, the reference duplexer or duplexer is connected in series to the measurement target duplexer or duplexer, and the reference duplexer or duplexer reaches the measurement target. The total insertion loss is obtained for each channel, and the measurement target multiplexer or demultiplexer is obtained by subtracting the insertion loss of each channel of the reference demultiplexer or multiplexer from the total insertion loss for each channel. Multiplexer / demultiplexer characterized by calculating insertion loss A method of insertion loss measurement.

  According to this method, the insertion loss of each channel of the reference demultiplexer or multiplexer is obtained in advance, and then the multiplexer or demultiplexer to be measured is changed to the reference demultiplexer or multiplexer. Connect to find the total insertion loss for each channel. By subtracting the insertion loss obtained for reference (for reference) from the total insertion loss, the insertion loss of the multiplexer or duplexer to be measured can be obtained. As a result, the insertion loss of each channel can be obtained without performing the measurement for each channel individually for the measurement target multiplexer or demultiplexer. Therefore, it is possible to easily measure the insertion loss in each channel of the multiplexer or duplexer to be measured.

  According to the multiplexer / demultiplexer insertion loss measuring method of the present invention, when measuring the insertion loss of each channel of the target multiplexer / demultiplexer, the reference (reference) duplexer is measured. Alternatively, a multiplexer is prepared, and the insertion loss of each channel is obtained for reference in advance, and each of the multiplexers or duplexers to be measured is connected to the duplexer or multiplexer at that time. By calculating the total insertion loss of the channel and subtracting the reference insertion loss obtained in advance from this total insertion loss, it is possible to connect each of the multiplexers or demultiplexers to be measured without changing the connection on the multi-wavelength side. Since the insertion loss of the channel is obtained, it is possible to easily measure the insertion loss of each channel of the multiplexer / demultiplexer to be measured, and the number of multiplexers / demultiplexers to be measured. As the number increases, the measurement time and the burden of measurement work are reduced. Can.

  FIG. 1 shows a loss measurement process for a duplexer in the method for measuring the insertion loss of a multiplexer / demultiplexer according to an embodiment of the present invention. FIG. 2 shows a procedure for connecting a multiplexer and a duplexer according to the insertion loss measurement method of FIG.

  With reference to FIG. 2, the outline of the insertion loss measuring method of the multiplexer / demultiplexer according to the embodiment of the present invention will be described. When measuring the loss of the multiplexer, as shown in FIG. 2A, the coupler 2 (branching means) is connected to the wavelength tunable light source 1 via the optical fiber 21, and the optical fiber 24 is connected to one of the branched outputs. Is connected to a power meter 3 (PM1) as a first measuring means, and the other branch output is an output of the wavelength tunable light source 1 among a plurality of input terminals of the multiplexer 4 via an optical fiber 22. One corresponding to the wavelength of light is connected. A power meter 5 (PM 2) as a second measuring unit is connected to the output terminal of the multiplexer 4 through an optical fiber 23.

  When light having a wavelength λ1 is generated from the wavelength tunable light source 1, the optical fiber 22 is connected to the input terminal corresponding to the wavelength λ1 of the multiplexer 4, and the optical power at this time is measured by the power meters 3 and 5. When the optical power value P2 of the power meter 5 is subtracted from the optical power value P1 of the power meter 3, the loss of the multiplexer 4 at the wavelength λ1 can be calculated. Thereafter, in the same manner, light of wavelengths λ2,..., Λn is sequentially generated from the wavelength tunable light source 1, and each time the optical fiber 22 is connected to the other input terminal of the multiplexer 4, the optical power value P1. , P2 are measured, and the respective wavelengths of the multiplexer 4, that is, the losses in all the channels are calculated. This calculation can be performed using a computer or a dedicated arithmetic device. Alternatively, the person in charge may perform by writing.

  Next, as shown in FIG. 2B, the duplexer 6 is inserted and connected between the optical fiber 22 and the multiplexer 4. The same wavelength is connected between the output terminal of the duplexer 6 and the input terminal of the multiplexer 4. In this state, the wavelength of the output light of the wavelength tunable light source 1 is sequentially changed from λ1 to λ2,..., Λn, and the optical power is measured by the power meters 3 and 5 at each wavelength to calculate the loss of each channel. The loss in this case is the total insertion loss of the duplexer 6 and the multiplexer 4. Therefore, by subtracting the loss of the multiplexer 4 obtained in FIG. 2A, the loss of the duplexer 6 can be obtained.

  Furthermore, the case where it is desired to obtain the loss of the multiplexer 4 will be described. In this case, as shown in FIG. 2C, a duplexer 6 is connected instead of the multiplexer 4 in the configuration of FIG. Then, λ2,..., Λn are sequentially generated from the wavelength tunable light source 1, and each time the wavelength tunable light source 1 at each wavelength is changed while changing the connection between the optical fiber 23 and the output terminal of the duplexer 6. , And the optical power from the branching filter 6 are measured by the power meters 3 and 5, the loss in all the channels of the branching filter 6 can be calculated.

  Next, as shown in (b) of FIG. 2, the multiplexer 4 as the measurement object is inserted and connected between the duplexer 6 and the optical fiber 22. The input terminal of the multiplexer 4 is connected to the output terminal of the duplexer 6 (same channels are connected together). In this state, the wavelength of the output light of the wavelength tunable light source 1 is sequentially changed from λ1 to λ2,..., Λn, and the optical power is measured by the power meters 3 and 5 at each wavelength to calculate the loss of each channel. The loss in this case is the total insertion loss of the duplexer 6 and the multiplexer 4. Therefore, the loss of the multiplexer 4 can be obtained by subtracting the loss of the duplexer 6 obtained in (c) of FIG.

  As described above, first, the insertion loss of the reference (or reference) multiplexer 4 or the demultiplexer 6 is obtained for each wavelength (all channels), and then the demultiplexer 6 for which the insertion loss is to be obtained. Alternatively, if the multiplexer 4 is additionally connected as shown in FIG. 2B and the insertion loss of the known multiplexer 4 or duplexer 6 is subtracted from the loss calculation result based on the measurement, the duplexer 6 Alternatively, the insertion loss of the multiplexer 4 can be obtained.

  Therefore, if a multiplexer or a demultiplexer serving as a measurement reference is prepared for measurement and its loss is grasped in advance, it is not necessary to perform measurement for the reference thereafter. ), Simply insert and connect to the multiplexer or demultiplexer that is the measurement target (object to be measured) without changing the connection of the output terminal or input terminal of the measurement target. The loss of the wave duplexer or duplexer can be determined.

Since the multiplexer / demultiplexer and loss data prepared as the measurement reference can be used as is for the measurement object (measurement object) in other places, the measurement and loss for the reference are performed again. There is no need to calculate. The reference multiplexer / demultiplexer is used only at the time of measurement, and can be repeatedly used as a reference device after the measurement is completed .

  The inventor has compared and examined the measurement reproducibility of the conventional measurement method shown in FIG. 5 and the measurement method according to the embodiment of the present invention. As a result, the measurement reproducibility in the conventional method shown in FIG. 5 was ± 0.1 dB (depending on the reproduction accuracy of the optical switch 17), but the measurement reproducibility by the method of the present invention in FIG. It is ± 0.05 dB (measurement accuracy of the measuring device), and it has been found that double accuracy can be obtained by the method according to the embodiment of the present invention.

  Next, details of the measurement method according to the embodiment of the present invention will be described with reference to FIGS. 1 and 2. Here, it is assumed that the multiplexer is an object to be measured (measurement target). Further, the reference duplexer 6 has no insertion loss data, and it is assumed that measurement is performed and acquired. In FIG. 1, “S” in the figure means a step, and (1) to (5) in the figure correspond to (1) to (5) described below.

  (1) First, the branch output difference of the coupler 2 is measured and calculated. A coupler 2 is connected to the wavelength variable light source 1. The power meter 3 (PM1) is connected to the first branch output (branch on the optical fiber 24 side) of the coupler 2, the output of the wavelength tunable light source 1 is set to the wavelength λ1 of ch1, and the optical power (Lc1) at that time Is measured with a power meter 3. Further, the power meter 3 is switched to the second branch output of the coupler 2 (branch on the optical fiber 22 side), and the optical power at that time is maintained while keeping the output condition of the wavelength variable light source 1 the same as that of the optical fiber 24 side. (Lc2) is measured with the power meter 3. From these two measurement results, the branch output difference (Lc) of the coupler 2 can be calculated by the following calculation formula (S101).

                      Lc = Lc1-Lc2 (1)

  (2) Next, the variable wavelength light source 1, the coupler 2, the duplexer 6, and the power meters 3 and 5 are connected as shown in FIG. Then, the output of the wavelength tunable light source 1 is set to the wavelength of ch1, and the branch output (on the optical fiber 24 side) from the coupler 2 is measured (measured value: Lc1) with the power meter 3 (PM1). Further, the output from ch1 (the uppermost output terminal in the figure) of the reference duplexer 6 is measured by the power meter 5 (PM2) (measured value: Lch1), and the duplexer is calculated from the difference between these measured values. 6 ch1 reference loss (L1a) is calculated (S102).

              L1a = Lch1-Lc1 + Lc (2)

  (3) Next, the wavelength of the wavelength tunable light source 1 is sequentially set from the channel 1 to the other measurement channel (λ 2 → λ 3 →... → λn), and the output of the duplexer 6 is adjusted to each channel. The power meter 5 is sequentially connected to the terminal, and the branch output from the coupler 2 (measured values Lch2 to Lchn) and the output from each channel of the duplexer 6 (measured value: similar to the processing in (2) above). Lc2 to Lcn) are measured, and reference losses other than ch1 of the duplexer 6 (calculated values: L2a, L3a,..., Lna) are calculated from the difference between the measured values of these channels (S103). When it is determined that the measurement for all channels has been completed (S104), the process proceeds to S105.

Reference loss of channel 2: L2a = Lch2-Lc2 + Lc
Reference loss of channel 3: L3a = Lch3-Lc3 + Lc
・ ・
・ ・
・ ・
Reference loss of channel n: Lna = Lchn−Lcn + Lc (3)

  (4) Next, with respect to the connection of FIG. 2C, the multiplexer 4 which is a device under test is connected as shown in FIG. Then, the output of the wavelength tunable light source 1 is sequentially changed from the wavelength λ1 of ch1 to λ2,..., Λn, and the branch output from the coupler 2 is measured with the power meter 3 each time (measurement values: LchC1 to LchCn). At the same time, the output from the multiplexer 4 is measured by the power meter 5 (measured values: LchO1 to LchOn), and the total loss of the duplexer 6 and the multiplexer 4 is determined for each channel from the difference between these measured values. TL (calculated values = TL1, TL2,..., TLn) is calculated (S105).

Total loss of channel 1: TL1 = LchO1-LchC1 + Lc
Total loss of channel 2: TL2 = LchO2-LchC2 + Lc
・ ・
・ ・
・ ・
Total loss of channel n: TLn = LchOn−LchCn + Lc (4)

  (5) From the total loss (TL) of the duplexer 6 and the multiplexer 4 of each channel measured in the above (4), the reference loss (divided) of each channel measured in the above (2) or (3) The insertion loss (calculated values: L1, L2,..., Ln) of each channel of the multiplexer 4 to be measured is calculated by subtracting the insertion loss when only the wave filter 6 is connected (S106). . The insertion loss (L1 to Ln) of each channel of the multiplexer 4 to be measured thus obtained is as follows.

Insertion loss of channel 1: L1 = TL1-L1a
Insertion loss of channel 2: L2 = TL2-L2a
・ ・
・ ・
・ ・
Insertion loss of channel n: Ln = TLn−Lna (5)

  The above is the case where the measurement target (object to be measured) is the multiplexer 4, but when the duplexer 6 is the measurement target, the procedure is substantially the same as the procedure for measuring the loss of the multiplexer 4 described above. Done in First, after the loss of each channel is measured for the reference multiplexer 4 by the connection shown in FIG. 2A, the measurement target duplexer 6 is connected as shown in FIG. 2B. . In this state, each channel is measured, and the loss of each channel of the duplexer 6 that is the measurement target is calculated based on the difference between the measured value and the measured value of each channel in FIG.

  When the multiplexer 4 is for reference, a coupler (or splitter) can be used instead of the multiplexer.

It is a flowchart which shows the loss measurement process of the splitter in the insertion loss measuring method of the multiplexer and the splitter which concerns on embodiment of this invention. It is a connection diagram explaining the connection procedure of the multiplexer and the duplexer according to the insertion loss measuring method of FIG. It is a connection diagram which shows the structural example for implement | achieving the conventional insertion loss measuring method in a multiplexer. It is a connection diagram which shows the structural example for implement | achieving the conventional insertion loss measuring method in a splitter. It is a connection diagram which shows the other structural example for implement | achieving the conventional insertion loss measuring method in a splitter.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Wavelength variable light source 2 Coupler 3,5 Power meter 4 Wave multiplexer 6 Wave splitter 6 Wave splitter 21, 22, 23, 24 Optical fiber 11 Wavelength variable light source 12 Coupler 13, 15 Power meter 14 Wave multiplexer 16 Wave splitter 31, 32 , 33, 34 Optical fiber

Claims (5)

Insertion loss measurement method for a multiplexer / demultiplexer that measures the insertion loss of a multiplexer that multiplexes a plurality of optical signals having different wavelengths, or a demultiplexer that demultiplexes the wavelength-multiplexed optical signal for each wavelength. In
Find the insertion loss of each channel of the reference demultiplexer or multiplexer used only during measurement,
The reference demultiplexer or multiplexer is connected in series to the measurement target multiplexer or demultiplexer in a state where the same channels on the multi-wavelength side are connected to each other, and the reference demultiplexing is performed. For each channel, the total insertion loss from the measuring device or multiplexer to the measurement object is determined,
Subtracting the insertion loss of each channel of the reference demultiplexer or multiplexer from the total insertion loss for each channel to calculate the insertion loss of the measurement target multiplexer or demultiplexer The insertion loss measurement method for a multiplexer / demultiplexer.   The calculation of the insertion loss of the measurement target multiplexer / demultiplexer is performed together with the insertion loss of each channel of the reference demultiplexer / multiplexer and the first branch light and the first branch light of the branching unit. 2. The method of measuring insertion loss of a multiplexer / demultiplexer according to claim 1, wherein an output difference Lc from the branched light of 2 is subtracted from a total insertion loss for each channel.   The insertion loss of each channel of the reference demultiplexer or multiplexer is obtained by branching the output light from the wavelength tunable light source into two by the branching means, and measuring the optical power from the first branch by the first measurement. And measuring the optical power from the second branch to the reference demultiplexer or multiplexer, and whenever the channel of the wavelength tunable light source is changed, the reference demultiplexer or combiner is changed. The optical power of each channel on the multi-wavelength side of the device is measured by the second measuring means, and the measured value by the second measuring means is subtracted from the measured value by the first measuring means. The method of measuring insertion loss of a multiplexer / demultiplexer according to claim 1.   The insertion loss of each channel of the reference demultiplexer or multiplexer is obtained only for the first time, and thereafter, the insertion loss value obtained for the first time is used and remeasurement is not performed. 4. A method for measuring insertion loss of a multiplexer / demultiplexer according to 1 or 3. The first and second measuring means measure each of the optical powers using a power meter,
4. The method for measuring insertion loss of a multiplexer / demultiplexer according to claim 3, wherein the branching means forms the first branched light and the second branched light using a coupler.