Optical system capable of achieving frequency sweeping through cyclic cascaded stretching

An optical system capable of achieving frequency sweeping through cyclic cascaded stretching, comprising:

• an ultrafast pulsed laser;
• two couplers;
• a positive-dispersion cyclic stretching module;
• a negative-dispersion cyclic stretching module;
• a polarization-maintaining fiber;
• and
• a delay line;
• wherein the ultrafast pulsed laser is in communication with the two couplers through the polarization-maintaining fiber;
• a first end of the negative-dispersion cyclic stretching module is in communication with one of the two couplers through the polarization-maintaining fiber, a second end of the negative-dispersion cyclic stretching module is in communication with the other of the two couplers through the polarization-maintaining fiber, a first end of the positive-dispersion cyclic stretching module is in communication with one of the two couplers through the polarization-maintaining fiber, and a second end of the positive-dispersion cyclic stretching module is in communication with the other of the two couplers through the delay line;
• or the first end of the negative-dispersion cyclic stretching module is in communication with one of the two couplers through the polarization-maintaining fiber, the second end of the negative-dispersion cyclic stretching module is in communication with the other of the two couplers through the delay line, the first end of the positive-dispersion cyclic stretching module is in communication with one of the two couplers through the polarization-maintaining fiber, and a second end of the positive-dispersion cyclic stretching module is in communication with the other of the two couplers through the polarization-maintaining fiber;
• the positive-dispersion cyclic stretching module and the negative-dispersion cyclic stretching module each comprises a first optical switch, the two couplers, two erbium-doped fiber amplifiers (EDFAs), a chirped fiber Bragg grating (CFBG), a second optical switch, a third optical switch, a delay fiber as the delay line and the polarization-maintaining fiber;
• the first optical switch is in communication with one of the two couplers through the polarization-maintaining fiber;
• the two EDFAs are respectively in communication with two ends of the CFBG through the polarization-maintaining fiber;
• one of the two EDFAs is in communication with one of the two couplers through the polarization-maintaining fiber;
• and the other of the two EDFAs is in communication with the other of the two couplers through the polarization-maintaining fiber and the delay fiber;
• the two couplers are respectively in communication with the second optical switch through the polarization-maintaining fiber;
• and
• one of the two couplers that is arranged between the second optical switch and the delay fiber is in communication with the third optical switch through the polarization-maintaining fiber.