Optical demultiplexer, optical multi-/demultiplexer, and optical device

An optical device for transmitting/receiving light of first and second wavelengths, the optical device comprising:

• a multi-mode propagation portion allowing multi-mode propagation of light of the first and second wavelengths and separating powers of the light of first and second wavelengths by causing internal mode interference;
• an input portion for inputting light to the multi-mode propagation portion from such an input position as to cause separation of the powers of light in the multi-mode propagation portion;
• first and second output portions for outputting the light of first and second wavelengths from the multi-mode propagation portion via such positions on an output end face as to cause separation of the powers of the light of first and second wavelengths and maximize an extinction ratio indicating the size of the power of light of a desired wavelength with respect to the power of light of a wavelength to be cut off;
• a first optical element for receiving and/or emitting light of the first wavelength, the first optical element being provided at an output end of the first output portion;
• and
• a second optical element for receiving and/or emitting light of the second wavelength, the second optical element being provided at an output end of the second output portion.

An optical demultiplexer for separating input wavelength-multiplexed light of n types of different wavelengths, where n is a natural integer, the optical demultiplexer comprising:

• a multi-mode propagation portion allowing multi-mode propagation of the input wavelength-multiplexed light of n types of different wavelengths and separating powers of the light of n types of different wavelengths by causing internal mode interference;
• an input portion for inputting light to the multi-mode propagation portion from such an input position as to cause separation of the powers of light in the multi-mode propagation portion;
• and
• n output portions for outputting the light of n types of different wavelengths from the multi-mode propagation portion via such positions on an output end face as to cause separation of the powers of the light of n types of different wavelengths and maximize an extinction ratio indicating the size of the power of light of a desired wavelength with respect to the power of light of a wavelength to be cut off.

An optical multi-demultiplexer for combining/separating light of first and second wavelengths, the optical multi-demultiplexer comprising:

• a multi-mode propagation portion allowing multi-mode propagation of the light of first and second wavelengths and separating powers of the light of first and second wavelengths by causing internal mode interference;
• an input portion for inputting light to the multi-mode propagation portion from such an input position as to cause separation of the powers of light in the multi-mode propagation portion;
• and
• first and second output portions for outputting the light of first and second wavelengths from the multi-mode propagation portion via such positions on an output end face as to cause separation of the powers of the light of first and second and maximize an extinction ratio indicating the size of the power of light of a desired wavelength with respect to the power of light of a wavelength to be cut off.

An optical multi-demultiplexer for combining/separating light of n types of different wavelengths, where n is a natural integer, the optical multi-demultiplexer comprising:

• a multi-mode propagation portion allowing multi-mode propagation of the light of n types of different wavelengths and separating powers of the light of n types of different wavelengths by causing internal mode interference;
• an input portion for inputting light to the multi-mode propagation portion from such an input position as to cause separation of the powers of light in the multi-mode propagation portion;
• and
• n output portions for outputting the light of n types of different wavelengths from the multi-mode propagation portion via such positions on an output end face as to cause separation of the powers of the light of n types of different wavelengths and maximize an extinction ratio indicating the size of the power of light of a desired wavelength with respect to the power of light of a wavelength to be cut off.

An optical device for adjusting wavelength-multiplexed light of n types of wavelengths, where n is a natural integer, the optical device comprising:

• a demultiplexing section for separating the light of n types of wavelengths;
• a multiplexing section for combining the light of n types of wavelengths;
• and
• n adjusting sections for adjusting light of the n types of wavelengths separated by the demultiplexing section and inputting the light of then types of wavelengths to the multiplexing section,
• wherein the demultiplexing section includes a demultiplexer multi-mode propagation portion allowing multi-mode propagation of the light of n types of wavelengths and separating powers of the light of n types of wavelengths by causing internal mode interference,
• wherein the multiplexing section includes a multiplexer multi-mode propagation portion allowing multi-mode propagation of the light of n types of wavelengths and combining powers of light of the n types of wavelengths by causing internal mode interference, and
• whereininthecasewherei=0,1, . . . ,n and k=1, 2, . . . ,n−1, when a phase difference between i′th- and i+1′th-order modes of a k′th wavelength λk is θk and a phase difference between i′th- and i+1′th-order modes of a k+1′th wavelength λk+1 is θk+1, each of the demultiplexer and multiplexer multi-mode propagation portions has such an optical path length in a propagation direction as to cause a difference between θk and θk+1 to be in the range of mπ±π/2, where m is a natural integer.

An optical device having an add/drop function of extracting one of two wavelengths multiplexed in light and recombining the two wavelengths, the optical device comprising:

• a demultiplexer for separating light of the two wavelengths;
• a multiplexer for combining light of the two wavelengths;
• a relay waveguide for relaying light of a first wavelength in wavelength-multiplexed light to the multiplexer, the relay waveguide being connected to the output side of the demultiplexer;
• a drop waveguide for guiding light of a second waveguide in the wavelength-multiplexed light to the outside of the demultiplexer, the drop waveguide being connected to the output side of the demultiplexer;
• and
• an add waveguide for guiding the light of the second wavelength back into the demultiplexer and relaying the light to the multiplexer,
• wherein the demultiplexer includes a demultiplexer multi-mode propagation portion allowing multi-mode propagation of light of the first and second wavelengths and separating powers of the light of the first and second wavelengths by causing internal mode interference,
• wherein the multiplexer includes a multiplexer multi-mode propagation portion allowing multi-mode propagation of the light of the first and second wavelengths and combining the powers of the light of the first and second wavelengths by causing internal mode interference, and
• wherein in the case where a phase difference between zero- and first-order modes of the first wavelength is θ1 and a phase difference between zero- and first-order modes of the second wavelength is θ2, each of the demultiplexer and multiplexer multi-mode propagation portions has such an optical path length in a propagation direction as to cause a difference between θ1 and θ2 to be in the range of mπ±π/2, where m is a natural integer.

An optical demultiplexer for separating, into two groups of wavelengths, input wavelength-multiplexed light of 2n types of different wavelengths λ1, . . . , λ2n, where n is a natural integer, the optical demultiplexer comprising:

• a multi-mode propagation portion allowing multi-mode propagation of light of the 2n types of different wavelengths in the input wavelength-multiplexed light and separating powers of light of the two groups of wavelengths by causing internal mode interference;
• an input portion for inputting light to the multi-mode propagation portion from such an input position as to cause separation of powers of light in the multi-mode propagation portion;
• and
• two output portions for outputting the light of the two groups of wavelengths from such positions as to cause separation of the powers of the light of the two groups of wavelengths,
• wherein the two groups of wavelengths consist of the group of odd-numbered multiplexed wavelengths and the group of even-numbered multiplexed wavelengths.

An optical demultiplexer for separating input wavelength-multiplexed light of first and second wavelengths, the optical demultiplexer comprising:

• a first multi-mode propagation portion for separating powers of light of third and fourth wavelengths by causing internal mode interference, the third wavelength being offset from the first wavelength by a prescribed wavelength, the fourth wavelength being offset from the second wavelength by a prescribed wavelength,
• an input portion for inputting light to the first multi-mode propagation portion from such an input position as to cause separation of powers of light in the first multi-mode propagation portion;
• a first output portion provided to an output end face of the first multi-mode propagation portion in such a position as to cause separation of the powers of light of the third and fourth wavelengths and maximize an extinction ratio indicating the size of the power of light of the fourth wavelength with respect to the power of light of the third wavelength;
• a second output portion provided to the output end face of the first multi-mode propagation portion in such a position as to cause separation of the powers of light of the third and fourth wavelengths and maximize the extinction ratio indicating the size of the power of light of the fourth wavelength with respect to the power of light of the third wavelength;
• second and third multi-mode propagation portions each separating powers of light of fifth and sixth wavelengths by causing internal mode interference, the fifth wavelength being offset from the first wavelength by a prescribed wavelength in a direction opposite to a direction of the offset of the third wavelength, the sixth wavelength being offset from the second wavelength by a prescribed wavelength in a direction opposite to a direction of the offset of the fourth wavelength;
• a third output portion provided to an output end face of the second multi-mode propagation portion in such a position as to cause separation of powers of light of the fifth and sixth wavelengths and maximize the extinction ratio indicating the size of the power of light of the sixth wavelength with respect to the power of light of the fifth wavelength;
• and
• a fourth output portion provided to an output end face of the third multi-mode propagation portion in such a position as to cause separation of the powers of light of the fifth and sixth wavelengths and maximize the extinction ratio indicating the size of the power of light of the sixth wavelength with respect to the power of light of the fifth wavelength.