PMD emulator
A PMD emulator configured by connecting in this order: an input-side optical fiber 71 for receiving light to be measured; a first polarization rotating portion 73 including M DGD sections 76 (M is an integer equal to or more than 2) concatenated by (M−1) polarization rotators 80 , one DGD section being arranged at each end of said first polarization rotating portion; an arbitrary-arbitrary polarization controller 75 for changing any state of polarization into any other state of polarization, a second PMD rotating portion 74 configured in the same way as the first polarization rotating portion 73 an output-side optical fiber for outputting the light to be measured.
1. A PMD emulator comprising:
an input-side optical fiber for receiving light to be measured;
an output-side optical fiber for outputting the light to be measured;
a first polarization rotating portion including M DGD sections (M is an integer equal to or more than 2) and (M−1) polarization rotators alternatively concatenated with M DGD sections, one DGD section being arranged at each end of said first polarization rotating portion;
a second polarization rotating portion including N DGD sections (N is an integer equal to or more than 2) and (N−1) polarization rotators alternatively concatenated with N DGD sections, one DGD section being arranged at each end of said second polarization rotating portion; and
an arbitrary-arbitrary polarization controller for changing any state of polarization into any other state of polarization;
wherein said input-side optical fiber is connected to a DGD section at an input side of said first polarization rotating portion, a DGD section at an output side of said first polarization rotating portion being connected to a connecting portion at an input side of said arbitrary-arbitrary polarization controller, a connecting portion at an output side of said arbitrary-arbitrary polarization controller being connected to a DGD section at an input side of said second rotating portion, and a DGD section at an output side of said second polarization rotating portion being connected to said output-side optical fiber.
2. The PMD emulator as claimed in claim 1 , wherein the polarization controller is configured as a polarization rotator connected to each end of a polarization shifter.
3. The PMD emulator as claimed in claim 1 , wherein M is 2 and N is 2.
4. The PMD emulator as claimed in any one of claims 1 through 3 , wherein said polarization rotators are controlled based on a control parameter obtained by a simulation thereby to generate a desired PMD value.
5. The PMD emulator as claimed in any one of claims 1 through 3 , wherein said polarization rotators are controlled to change an average DGD without changing DGD characteristics of the DGD sections.
6. The PMD emulator as claimed in claim 1 , wherein each of the first and second polarization rotating portions includes 40 or more DGD sections connected at a random relative angle to each other and a temperature controlling means for changing a temperature as a whole.
7. The PMD emulator as claimed in claim 6 , wherein each DGD section has different DGD in accordance with normal distribution.
8. The PMD emulator as claimed in claim 7 , wherein standard deviation of the normal distribution is 20% of an average of the normal distribution.
9. The PMD emulator as claimed in any one of claims 6 through 8 , wherein the DGD sections are polarization maintaining fibers or uniaxial birefringent crystals.