Method for compensating polarization mode dispersion occurring optical transmission fiber and apparatus therefor

An apparatus for compensating polarization mode dispersion (PMD) occurring in optical transmission fiber, the apparatus comprising:

• a polarization scrambler installed at a transmission terminal, for exciting polarization of input light to optical transmission fiber with equal probability in all directions and transmitting the scrambled light to an the transmission line;
• a polarization controller (PC) for transforming states and directions of polarization components of an optical signal received from the optical transmission line;
• a polarization beam splitter (PBS) for separating two orthogonal polarization components of the optical signal output from the PC, for transmitting a first polarization component to an signal output path and transmitting a second polarization component to a monitoring path;
• and
• a compensation controller for controlling the PC using the electrical spectrum of the optical signal transmitted to the monitoring path so that the two orthogonal polarization components of the optical input signal to the PBS are aligned to two axes of the PBS.

A method for compensating polarization mode dispersion (PMD) occurring in optical transmission fiber, the method comprising:

• (a) transforming states and directions of polarization components of an optical signal received from the optical transmission line;
• (b) rotating the polarization components of the optical signal output from the PC;
• (c) separating two orthogonal polarization components of the optical signal output from the polarization rotator so that a first polarization component is transmitted to an signal output path and a second polarization component is transmitted to a monitoring path;
• (d) controlling the PC using the electrical spectrum of the optical signal transmitted to the monitoring path so that the two orthogonal polarization components of the optical input signal to the PBS are aligned to two axes of the PBS;
• and
• (e) controlling the polarization rotator by comparing an optical power of the first polarization component transmitted to the signal output path with an optical power of the second polarization component transmitted to the monitoring path.

A method for compensating polarization mode dispersion (PMD) occurring in optical -transmission fiber, the method comprising:

• (a) exciting polarization of input light to optical transmission fiber with equal probability in all directions and transmitting the scrambled light to the transmission line;
• (b) transforming states and directions of polarization components of an optical signal received from the optical transmission line;
• (c) separating two orthogonal polarization components of the optical signal output from the PC so that a first polarization component is transmitted to an signal output path and a second polarization component is transmitted to a monitoring path;
• and
• (d) controlling the PC using the electrical spectrum of the optical signal transmitted to the monitoring path so that the two orthogonal polarization components of the optical input signal to the PBS are aligned to two axes of the PBS.

A method for compensating polarization mode dispersion (PMD) occurring in optical transmission fiber, the method comprising:

• (a) transforming states and directions of polarization components of an optical signal received from the optical transmission line;
• (b) rotating the polarization components of the optical signal output from the PC;
• (c) separating two orthogonal polarization components of the optical signal output from the polarization rotator so that a first polarization component is transmitted to an output path and a second polarization component is transmitted to a monitoring path;
• (d) detecting the band-pass filtered electrical power at the predetermined frequency satisfying the previously described principle of operation;
• (e) controlling the PC so that the two orthogonal polarization components of the optical input signal to the PBS are aligned to two axes of the PBS until the detected electrical power is converged on a minimum value;
• and
• (f) controlling the polarization rotator so that a polarization component having a larger optical power between the first and second polarization components that are separated by the PBS is output, once the detected electrical power is converged on a minimum value.

A method for compensating polarization mode dispersion (PMD) occurring in optical transmission fiber, the method comprising:

• (a) exciting polarization of input light to optical transmission fiber with equal probability in all directions and transmitting the scrambled light to the transmission line;
• (b) transforming states and directions of polarization components of an optical signal received from the optical transmission line;
• (c) separating two orthogonal polarization components of the optical signal output from the PC so that a first polarization component is transmitted to an output path and a second polarization component is transmitted to a monitoring path;
• (d) detecting the band-pass filtered electrical power at the predetermined frequency satisfying the previously described principle of operation;
• and
• (e) controlling the PC so that the two orthogonal polarization components of the optical input signal to the PBS are aligned to two axes of the PBS until the detected electrical power is converged on a minimum value.