JP5415467B2 - PDL measuring instrument and PDL measuring method - Google Patents

Description

  The present invention relates to a PDL measuring device and a PDL measuring method for measuring the wavelength dependence of polarization dependent loss (PDL) of a system under measurement.

  As a PDL of a system to be measured, a method is known in which light after transmission through the system to be measured is measured using a polarization scrambling method (polarization scanning method) or a Mueller method (Non-Patent Document 1).

  Polarization scrambling (polarization scanning) is a method in which the polarization state (SOP: State of Polarization) of input light is randomly scrambled by the polarization controller and input to the system under measurement to create all SOPs. The PDL is directly measured by the difference between the maximum value and the minimum value of the output light intensity. The Mueller method is a method of mathematically measuring PDL by the Mueller-Stokes method using power measurement values in four types of input polarization (horizontal, vertical, +45 degrees, clockwise circle) defined by the polarization controller. It is.

  In addition, the measurement of the wavelength dependence of the PDL of the system to be measured is possible by a configuration in which the wavelength switching timing of the PDL meter incorporating the above PDL measurement method and the wavelength variable light source is synchronized. 5 and 6 show a configuration example of a conventional PDL measuring device for measuring the PDL wavelength dependency.

  In the configuration example 1 of the PDL measuring device shown in FIG. 5, the wavelength tunable light source 11, the polarization controller 12, the system under test 13, and the PDL meter 14 are connected in this order, and the wavelength tunable light source 11 and the PDL measuring device 14 are connected by a communication cable. In this configuration, the wavelength switching timing of the wavelength tunable light source 11 is notified to the PDL measuring device 14 and the wavelength dependence of the PDL is measured (Non-Patent Document 2).

  In the configuration example 2 of the PDL measuring device shown in FIG. 6, the wavelength variable light source 11, the polarization controller 12, the system under test 13, and the PDL meter 14 are connected in this order, and the synchronization signal is superimposed on the measurement light output from the wavelength variable light source 11 In this configuration, the PDL meter 14 measures the wavelength dependence of the PDL in synchronization with the wavelength switching timing of the wavelength tunable light source 11 obtained from the synchronization signal (Non-patent Document 3).

Agilent Application Note, “Polarization Dependent Loss Measurement of Passive Optical Components”, http://cp.literature.agilent.com/litweb/pdf/5988-1232EN.pdf Thorlabs, “PMD / PDL Measurement System”, http://www.thorlabs.de/catalogPages/JP-Thorlabs%20Catalog/Thorlabs JP% 20987.pdf Agilent White Paper, “Fibre Performance Evaluation in Advanced Optical Networks Part 2 Polarization Mode Dispersion”, http://cp.literature.agilent.com/litweb/pdf/5989-1475EN.pdf

  In order to measure the wavelength dependence of PDL with the PDL measuring device shown in FIG. 5, it is necessary to synchronize between the transmission side and the reception side, but due to the difference between the optical transmission line and the route through the communication cable, the long distance transmission line In this case, it was difficult to measure the wavelength dependence of PDL on the opposite side.

  In order to measure the wavelength dependence of PDL with the PDL measuring device shown in FIG. 6, the synchronization signal attenuates due to the influence of noise during PDL measurement in a long-distance transmission line, and synchronization cannot be reliably established. There was a problem.

  The present invention provides a PDL measuring instrument and a PDL measuring method capable of reliably detecting the wavelength switching timing of a wavelength tunable light source on the transmitting side with a PDL meter on the receiving side and measuring the wavelength dependence of the PDL of the system under measurement. The purpose is to do.

  According to a first aspect of the present invention, there is provided a PDL measuring device for measuring the wavelength dependence of the PDL of the system to be measured, a wavelength variable light source that outputs measurement light of a plurality of wavelengths one wavelength at a time, and a measurement light output from the wavelength variable light source A polarization controller that changes the polarization state and inputs it to the system to be measured; a monitoring means that inputs the measurement light output from the system to be measured, demultiplexes it into each wavelength, and monitors the measurement light at each wavelength; A PDL meter that inputs measurement light output from the measurement target system, detects the timing at which the wavelength of the measurement light switches according to the monitoring result of the monitoring means, and measures the PDL of the measurement target system at each wavelength is provided.

  The monitoring means in the PDL measuring device according to the first aspect of the invention receives a measurement light output from the system under measurement, and demultiplexes the wavelength into n wavelengths (n is an integer of 2 or more), and a wavelength demultiplexer The power of the measurement light of each wavelength demultiplexed by n is monitored, and the n power meters notified to the PDL meter and the measurement light of each wavelength demultiplexed by the wavelength demultiplexer are combined, and the system to be measured And a wavelength multiplexer that is input to the PDL meter as measurement light output from the PDL meter, and the PDL meter recognizes the wavelength of the measurement light when the power of each wavelength detected by the n power meters exceeds a threshold value In this configuration, the PDL of the system under measurement at the wavelength is measured.

  The monitoring means in the PDL measuring device according to the first aspect of the invention splits the measuring light output from the system under measurement into two branches, one of which is input to the PDL meter, and the other measurement branched by the optical branching device. Inputs light, monitors the power of the wavelength demultiplexer that demultiplexes into n wavelengths (n is an integer of 2 or more), and the measurement light of each wavelength demultiplexed by the wavelength demultiplexer, and notifies the PDL meter n power meters, the PDL meter recognizes the wavelength of the measurement light at the timing when the power of each wavelength detected by the n power meters exceeds the threshold, and determines the PDL of the system under measurement at the wavelength. It is the structure to measure.

  According to a second aspect of the present invention, there is provided a PDL measuring device that measures the wavelength dependence of the PDL of the system under measurement, a wavelength variable light source that outputs measurement light of a plurality of wavelengths in order of wavelengths, and measurement light output from the wavelength variable light source A polarization controller that changes the polarization state of the signal to be input to the system to be measured and a measurement light output from the system to be measured and demultiplexes into m wavelengths (m is an integer of 2 or more) at a predetermined wavelength period. The monitor means for monitoring the measurement light of each wavelength and the measurement light output from the system to be measured are input, and the timing at which the wavelength of the measurement light is sequentially switched at a predetermined wavelength period is detected from the monitoring result of the monitor means, A PDL meter that measures the PDL of the system under measurement at each wavelength is provided.

  The monitoring means in the PDL measuring device according to the second aspect of the invention receives a measurement light output from the system under measurement, and a periodic wavelength demultiplexer for demultiplexing into m wavelengths at a predetermined wavelength period, and a periodic wavelength demultiplexing Monitoring the power of the measurement light of each wavelength demultiplexed by the analyzer, and combining the m power meters to notify the PDL meter and the measurement light of each wavelength demultiplexed by the periodic wavelength demultiplexer, An optical coupler that is input to the PDL meter as measurement light output from the system under measurement, and the PDL meter is a timing at which the power of each wavelength sequentially detected by the m power meters at a predetermined wavelength period exceeds a threshold value. In this configuration, the wavelength of the measurement light is recognized and the PDL of the system under measurement at the wavelength is measured.

  The monitoring means in the PDL measuring device according to the second invention comprises two branches of the measuring light output from the system under test, one of which is input to the PDL meter, and the other measurement branched by the optical branching device. Inputs light, monitors the power of the periodic wavelength demultiplexer that demultiplexes into m wavelengths at a predetermined wavelength period, and the measurement light power of each wavelength demultiplexed by the periodic wavelength demultiplexer, and notifies the PDL meter The PDL meter recognizes the wavelength of the measurement light at a timing when the power of each wavelength sequentially detected by the m power meters at a predetermined wavelength period exceeds a threshold, and the wavelength It is the structure which measures PDL of the to-be-measured system in.

  According to a third aspect of the present invention, in the PDL measurement method for measuring the wavelength dependence of the PDL of the system under measurement, measurement light having a plurality of wavelengths is output from the wavelength variable light source one wavelength at a time, and the measurement light output from the wavelength variable light source Change the polarization state with the polarization controller and input it to the system to be measured, input the measurement light output from the system to be measured to the monitoring means, demultiplex it into each wavelength, and monitor the measurement light at each wavelength, The measurement light output from the measured system is input to the PDL meter, the timing at which the wavelength of the measured light is switched is detected based on the monitoring result of the monitoring means, and the measured system PDL is measured at each wavelength.

  4th invention is the PDL measuring method which measures the wavelength dependence of PDL of a to-be-measured system, outputs the measurement light of several wavelengths from a wavelength variable light source in order of a wavelength, and the measurement light output from a wavelength variable light source The polarization state is changed by the polarization controller and input to the system to be measured, and the measurement light output from the system to be measured is input to the monitor means, and m wavelengths with a predetermined wavelength period (m is an integer of 2 or more) The measurement light of each wavelength is monitored and the measurement light output from the system under test is input to the PDL meter, and the timing at which the wavelength of the measurement light is sequentially switched at a predetermined wavelength period according to the monitoring result of the monitoring means. Detect and measure the PDL of the system under measurement at each wavelength.

  The present invention can measure the PDL at each wavelength by detecting the timing at which the wavelength of the measurement light output from the measured system is switched between the measured system and the PDL meter. That is, the PDL measurement synchronized with the wavelength switching timing of the measurement light detected in the receiving system subsequent to the measured system can reliably measure the wavelength dependence of the PDL even if the measured system is a long-distance transmission line. Can do.

It is a figure which shows Example 1 of the PDL measuring device of this invention. It is a figure which shows Example 2 of the PDL measuring device of this invention. It is a figure which shows Example 3 of the PDL measuring device of this invention. It is a figure which shows Example 4 of the PDL measuring device of this invention. It is a figure which shows the structural example 1 of the conventional PDL measuring device. It is a figure which shows the structural example 2 of the conventional PDL measuring device.

FIG. 1 shows a configuration example of Embodiment 1 of the PDL measuring device of the present invention.
In FIG. 1, the transmission system in the previous stage of the system under measurement 13 includes a wavelength tunable light source 11 and a polarization controller 12 that output measurement light having wavelengths λ _{1 to} λ _n one wavelength at a predetermined time interval. The receiving system at the subsequent stage of the system under measurement 13 is connected to each of the wavelength demultiplexer 21 having an output port for demultiplexing to wavelengths λ _{1 to} λ _n and the _n output ports of the wavelength demultiplexer 21 to each wavelength. N power meters (PM) 22-1 to 22-n for monitoring the power of the measurement light, and a wavelength multiplexer 23 for inputting the passing light of each power meter to the n input ports and combining them. The PDL meter 14 is connected to the output port of the wavelength multiplexer 23. The n power meters 22-1 to 22-n and the PDL meter 14 are connected by a communication cable in the reception system, and the power detection value of the measurement light of each wavelength is notified to the PDL meter 14.

  The wavelength tunable light source 11 is set so that the wavelength of the measurement light to be output is automatically switched at a time interval T longer than the time t at which the PDL meter 14 finishes measuring one wavelength. The PDL of each wavelength is measured by the PDL meter 14 using the polarization scramble method or the Mueller method.

  Here, the PDL meter 14 sets a threshold value Pth for the power detection values of the n power meters 22-1 to 22-n, and the timing at which each power detection value corresponding to each wavelength exceeds the threshold value Pth, that is, for each wavelength. The timing when the measurement light is input is detected.

When measuring the PDL of the system under test 13 for the wavelength λ ₁ of the wavelength tunable light source 11, when the power detection value of the power meter 22-1 corresponding to the wavelength λ ₁ exceeds the threshold value Pth, the PDL meter 14 measures. PDL measurement of system 13 is started. When the wavelength of the wavelength tunable light source 11 is switched to λ ₂ after the elapse of time T, the detected value of the power meter 22-1 corresponding to the wavelength λ ₁ in the previous measurement becomes equal to or less than the threshold value Pth, and the power corresponding to the wavelength λ ₂ The detection value of the meter 22-2 is equal to or greater than the threshold value Pth. Immediately after this change in the power detection value is detected by the PDL meter 14, PDL measurement of the system under test 13 for the next wavelength λ ₂ is started. Similarly, by measuring the PDL of the measured system 13 monitors the power detection value of the power meter 22-3~22-n for lambda _n from the wavelength lambda _3, the wavelength dependency of the PDL of the measuring system 13 Can be measured.

FIG. 2 shows a configuration example of Embodiment 2 of the PDL measuring device of the present invention.
The feature of the second embodiment is that, instead of the wavelength demultiplexer 21, the power meters 22-1 to 22-n, and the wavelength multiplexer 23 for monitoring the measurement light of the first embodiment, a periodic demultiplexing characteristic is used. A periodic wavelength demultiplexer 24, power meters 22-1 to 22-m corresponding to the number m of demultiplexed wavelengths in one cycle, and an optical coupler 25 that multiplexes the light passing through each power meter. is there. The periodic wavelength demultiplexer 24 shown here has a configuration (m = 2) in which wavelengths λ ₁ , λ ₂ ,..., Λ _2n−1 , λ _2n are alternately demultiplexed into two output ports (m = 2). Measurement light of odd-numbered wavelengths λ ₁ , λ ₃ ,..., Λ _2n-1 is input to 22-1, and even-numbered wavelengths λ ₂ , λ _{4 ,.} Measurement light is input.

The wavelength tunable light source 31 sequentially outputs measurement light having wavelengths λ ₁ , λ ₂ ,..., Λ _2n−1 , λ _2n at predetermined time intervals. When measuring the PDL of the system under test 13 for the wavelength λ ₁ with the PDL meter, when the power detection value of the power meter 22-1 exceeds the threshold Pth, the PDL meter starts the PDL measurement of the system under test 13 To do. When the wavelength of the wavelength tunable light source 11 is switched to λ ₂ after the elapse of T time, the power detection value of the power meter 22-1 corresponding to the wavelength λ ₁ in the previous measurement becomes equal to or less than the threshold value Pth and corresponds to the wavelength λ ₂ . The power detection value of the power meter 22-2 becomes equal to or greater than the threshold value Pth. Immediately after this change in the power detection value is detected by the PDL meter 14, PDL measurement of the system under test 13 for the next wavelength λ ₂ is started. Similarly, the detection values of the power meters 22-1 to 22-2 are alternately monitored, and the PDL of the measured system 13 with respect to the wavelengths λ ₃ to λ _2n is measured, whereby the PDL of the measured system 13 depends on the wavelength. Sex can be measured.

  As such a periodic wavelength demultiplexer 21, a WSS (wavelength selective switch), an optical interleaver, an AWG (arrayed waveguide diffraction grating), or the like can be used.

FIG. 3 shows an example of the configuration of Embodiment 3 of the PDL measuring device of the present invention.
In FIG. 3, the transmission system upstream of the system under test 13 is the same as that of the first embodiment. The receiving system at the subsequent stage of the system under measurement 13 branches the measurement light output from the system under measurement 13 and inputs one of them to the PDL meter 14 and the other measurement light branched from the wavelength λ ₁ to. A wavelength demultiplexer 21 having an output port for demultiplexing to λ _n and n power meters (PM) connected to each of the n output ports of the wavelength demultiplexer 21 to monitor the power of measurement light of each wavelength ) 22-1 to 22-n. The n power meters 22-1 to 22-n and the PDL meter 14 are connected by a communication cable in the reception system, and the power detection value of the measurement light of each wavelength is notified to the PDL meter 14.

  Unlike the configuration of the first embodiment, the means for monitoring the measurement light of each wavelength is connected via the optical coupler 26, but the principle of measuring the wavelength dependence of the PDL of the system under test 13 is the first embodiment. It is the same as that of the structure.

FIG. 4 shows a configuration example of Embodiment 4 of the PDL measuring device of the present invention.
The feature of the fourth embodiment is that, instead of the periodic wavelength demultiplexer 24 and the power meters 22-1 to 22-n for monitoring the measurement light of the third embodiment, the periodic demultiplexing is performed as in the second embodiment. The configuration uses a periodic wavelength demultiplexer 24 having characteristics and power meters 22-1 to 22-m corresponding to the number m of demultiplexed wavelengths in one cycle. The periodic wavelength demultiplexer 24 shown here has a configuration (m = 2) in which wavelengths λ ₁ , λ ₂ ,..., Λ _2n−1 , λ _2n are alternately demultiplexed into two output ports (m = 2). Measurement light of odd-numbered wavelengths λ ₁ , λ ₃ ,..., Λ _2n-1 is input to 22-1, and even-numbered wavelengths λ ₂ , λ _{4 ,.} Measurement light is input.

  Unlike the configuration of the second embodiment, the means for monitoring the measurement light of each wavelength is connected via the optical coupler 26, but the principle for measuring the wavelength dependence of the PDL of the system under test 13 is the second embodiment. It is the same as that of the structure.

DESCRIPTION OF SYMBOLS 11 Variable wavelength light source 12 Polarization controller 13 System to be measured 14 PDL meter 21 Wavelength demultiplexer 22 Power meter 23 Wavelength multiplexer 24 Periodic wavelength demultiplexer 25 Optical coupler 26 Optical coupler

Claims (8)

In a PDL measuring device that measures the wavelength dependence of the polarization dependent loss (hereinafter referred to as PDL) of the system under measurement,
A variable wavelength light source that outputs measurement light of a plurality of wavelengths one by one;
A polarization controller that changes the polarization state of the measurement light output from the wavelength tunable light source and inputs it to the system under measurement;
Monitoring means for inputting the measurement light output from the measurement target system, demultiplexing the measurement light into each wavelength, and monitoring the measurement light of each wavelength;
A PDL meter that inputs the measurement light output from the measurement target system, detects a timing at which the wavelength of the measurement light is switched based on a monitoring result of the monitoring unit, and measures the PDL of the measurement target system at each wavelength; A PDL measuring device comprising: The PDL measuring device according to claim 1,
The monitoring means includes
A wavelength demultiplexer that inputs the measurement light output from the measurement target system and demultiplexes the measurement light into n wavelengths (n is an integer of 2 or more);
N power meters that monitor the power of the measurement light of each wavelength demultiplexed by the wavelength demultiplexer and notify the PDL meter;
A wavelength multiplexer that multiplexes the measurement light of each wavelength demultiplexed by the wavelength demultiplexer and inputs the measurement light output from the measured system to the PDL meter;
The PDL meter is configured to recognize the wavelength of the measurement light at a timing when the power of each wavelength detected by the n power meters exceeds a threshold and measure the PDL of the system under measurement at the wavelength. A PDL measuring device characterized by that. The PDL measuring device according to claim 1,
The monitoring means includes
An optical splitter that splits the measurement light output from the system under test into two, and inputs one of the two into the PDL meter;
A wavelength demultiplexer that inputs the other measurement light branched by the optical demultiplexer and demultiplexes into n wavelengths (n is an integer of 2 or more);
N power meters that monitor the power of the measurement light of each wavelength demultiplexed by the wavelength demultiplexer and notify the PDL meter;
The PDL meter is configured to recognize the wavelength of the measurement light at a timing when the power of each wavelength detected by the n power meters exceeds a threshold and measure the PDL of the system under measurement at the wavelength. A PDL measuring device characterized by that. In a PDL measuring device that measures the wavelength dependence of the polarization dependent loss (hereinafter referred to as PDL) of the system under measurement,
A wavelength tunable light source that outputs measurement light of a plurality of wavelengths in the order of wavelengths;
A polarization controller that changes the polarization state of the measurement light output from the wavelength tunable light source and inputs it to the system under measurement;
Monitoring means for inputting the measurement light output from the system to be measured, demultiplexing it into m wavelengths (m is an integer of 2 or more) at a predetermined wavelength period, and monitoring the measurement light of each wavelength;
The measurement light output from the system to be measured is input, and the timing at which the wavelength of the measurement light is sequentially switched at a predetermined wavelength period is detected based on the monitoring result of the monitoring unit, and the PDL of the system to be measured at each wavelength is determined. A PDL measuring device comprising: a PDL meter for measuring. The PDL measuring device according to claim 4, wherein
The monitoring means includes
A periodic wavelength demultiplexer that inputs the measurement light output from the measurement target system and demultiplexes the measurement light into m wavelengths at a predetermined wavelength period;
M power meters for monitoring the power of measurement light of each wavelength demultiplexed by the periodic wavelength demultiplexer and notifying the PDL meter;
An optical coupler that multiplexes the measurement light of each wavelength demultiplexed by the periodic wavelength demultiplexer and inputs the measurement light output from the measured system to the PDL meter;
The PDL meter recognizes the wavelength of the measurement light at a timing when the power of each wavelength sequentially detected by the m power meters at a predetermined wavelength period exceeds a threshold, and the PDL of the measurement target system at the wavelength The PDL measuring device characterized by being configured to measure. The PDL measuring device according to claim 4, wherein
The monitoring means includes
An optical splitter that splits the measurement light output from the system under test into two, and inputs one of the two into the PDL meter;
A periodic wavelength demultiplexer that inputs the other measurement light branched by the optical demultiplexer and demultiplexes into m wavelengths at a predetermined wavelength period;
M power meters that monitor the power of the measurement light of each wavelength demultiplexed by the periodic wavelength demultiplexer and notify the PDL meter;
The PDL meter recognizes the wavelength of the measurement light at a timing when the power of each wavelength sequentially detected by the m power meters at a predetermined wavelength period exceeds a threshold, and the PDL of the measurement target system at the wavelength The PDL measuring device characterized by being configured to measure. In the PDL measurement method for measuring the wavelength dependency of the polarization dependent loss (hereinafter referred to as PDL) of the system under measurement,
Output measurement light of multiple wavelengths from wavelength tunable light source one wavelength at a time,
The polarization state of the measurement light output from the wavelength tunable light source is changed by a polarization controller and input to the measured system,
The measurement light output from the system under test is input to a monitoring means, demultiplexed into each wavelength, and monitoring the measurement light of each wavelength,
Inputting the measurement light output from the measured system into a PDL meter, detecting the timing at which the wavelength of the measured light is switched based on the monitoring result of the monitoring means, and measuring the PDL of the measured system at each wavelength; A PDL measurement method characterized by the above. In the PDL measurement method for measuring the wavelength dependency of the polarization dependent loss (hereinafter referred to as PDL) of the system under measurement,
Output measurement light of multiple wavelengths from the tunable light source in order of wavelength,
The polarization state of the measurement light output from the wavelength tunable light source is changed by a polarization controller and input to the measured system,
The measurement light output from the system to be measured is input to a monitoring unit, and is demultiplexed into m wavelengths (m is an integer of 2 or more) with a predetermined wavelength period, and the measurement light of each wavelength is monitored.
The measurement light output from the measurement target system is input to a PDL meter, and the timing at which the wavelength of the measurement light is sequentially switched at a predetermined wavelength period is detected based on the monitoring result of the monitoring means, and the measurement target system at each wavelength is detected. A method for measuring PDL, comprising:

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