Method of switching optical path, and apparatus thereof

A dualized line switching method, comprising:

• forming dualized lines by selectively connecting a second optical transmission line between first and second optical transmission devices separately from a first optical transmission line;
• being used in an optical communication switching system that comprises a first optical coupler means in which an optical signal I/O terminal of the first optical transmission device is connected to a first optical I/O terminal, and each of one sides of the first and second optical transmission lines is connected to second and third optical I/O terminals, a second optical coupler means in which an optical signal I/O terminal of the second optical transmission device is connected to a first optical I/O terminal, and each of the other sides of the first and second optical transmission lines is connected to second and third optical I/O terminals, a test light source that is connected to a fourth optical I/O terminal of the second optical coupler means and transmits pulse light in which an optical frequency is chirped, an optical measurement device that is connected to a fourth optical I/O terminal of the first optical coupler means and measures the pulse light output from the terminal, and a free space optics (FSO) device that is disposed on the second optical transmission line and compensates for a transmission time of pulse light transmitted through the line by expansion and contraction of a spatial optical line length;
• branching pulse light transmitted from the test light source by the second optical coupler means;
• multiplexing pulse light that has passed through the first optical transmission line and pulse light that has passed through the second optical transmission line by the first optical coupler means and then inputting the multiplexed pulse light to the optical measurement device;
• measuring an arrival time of pulse light passing through each optical transmission line and an interference waveform generated in an upper part of a pulse light waveform by using the optical measurement device;
• adjusting an optical line length of the FSO device so that the interference waveform becomes appropriate while matching the measured arrival time of pulse light;
• and
• switching an optical transmission signal between the first and second optical transmission devices from the first optical transmission line to the second optical transmission line.

The dualized line switching method according to claim

• wherein the test light source emits pulse light in which the optical frequency is chirped linearly or in a state close to a linear form, and
• wherein when the optical measurement device includes a Fast Fourier transformer (FFT) that performs Fast Fourier transform on an interference waveform generated in an upper part of the pulse light waveform, for an adjustment of the interference waveform, Fast Fourier transform is performed on the interference waveform,
• an optical line length of the FSO device is extended or contracted so that using a specific frequency component obtained at that time as a reference, the component moves to a frequency zero side,
• the optical line length is continuously extended or contracted again until the frequency component as the reference is measured, and
• the FSO device is adjusted so that the optical line length becomes half the extended or contracted length.

A free space optics (FSO) device, comprising:

• a pair of corner cubes disposed in a reference axial direction, facing each other;
• an optical system that irradiates light propagated along an optical line to the corner cubes and re-couples light reflected between the corner cubes to the optical line;
• an adjustment means that changes a distance between the corner cubes in the reference axial direction and adjusts a length of a reflection path of the light;
• a switching means that switches the number of times that the light is reflected between the corner cubes in a stepwise manner;
• and
• an evacuation means that evacuates the light to a sub-optical line in which an optical line length difference with the optical line is equal to or less than a specified value at the time of switching of the number of reflection times.

A free space optics (FSO) device, comprising:

• a pair of optical couplers that branch-couples an optical line between a pair of optical I/O ports to two systems of optical lines;
• a pair of optical attenuators that are disposed on the two systems of optical lines, respectively, and turn on or off optical transmission of the optical line of a corresponding system;
• a pair of optical switch circuits that are disposed on the two systems of optical lines, serially connect optical switches, which selectively switching-connect n (n is a natural number equal to or more than 2) systems, respectively, in multiple stages, and extends an optical line length in certain length unit by selectively connecting a plurality of optical fibers whose length is adjusted in certain length unit by each optical switch;
• and
• an optical line length adjustment means that is disposed on at least one of the two systems of optical lines and continuously varies an optical line length of the optical line of a corresponding system by the certain length or more.