An optical multiplexing and demultiplexing method of the present disclosure includes arranging, face to face, a polished surface of a coated optical fiber whose side surface is polished to a core or a vicinity of the core and a polished surface of an optical waveguide whose propagation constant varies in a longitudinal direction and whose side surface is polished to a core or a vicinity of the core, and aligning the polished surface of the coated optical fiber and the polished surface of the optical waveguide so that desired branching ratio is obtained from one end of the coated optical fiber to the end, distal to the former end, of the optical waveguide by relatively moving the polished surface of the coated optical fiber and the polished surface of the optical waveguide.

Fiber optic terminals and fiber optic networks having variable ratio couplers are disclosed. The fiber optic terminals comprise a shell having a portion of a variable ratio coupler disposed therein. The variable ratio coupler comprises an optical input, a first optical output, a second optical output and a control. The control may be adjusted for changing an output power level between the first optical output and the second optical output.

A variable wavelength filter includes: an input optical fiber; a diffraction grating that disperses input light from the input optical fiber; a variable mirror that has a reflective surface, wherein an angle of the reflective surface is adjustable, the variable mirror reflects the input light dispersed by the diffraction grating, the input light reflected by the variable mirror passes through a normal optical path, the input light that passes through the normal optical path has a wavelength band defined based on the angle of the reflective surface, and the defined wavelength band has a center wavelength corresponding to the angle of the reflective surface; an output optical fiber that outputs a portion of the input light that has passed through the normal optical path; and an optical detector disposed on a propagation path of the input light from the input optical fiber to the output optical fiber.

An adjustable wide-spectrum wavelength-insensitive directional coupler, comprising a substrate (100). A first-stage directional coupling structure (1), a phase-shifting structure (2), and a second-stage directional coupling structure (3) are sequentially connected and disposed on the substrate (100). The phase-shifting structure (2) comprises a phase-shifting curved waveguide, a phase-shifting straight waveguide (22), and a third modulation component (26), wherein the third modulation component (26) is disposed on the phase-shifting curved waveguide. One end of the phase-shifting curved waveguide is connected to an output end of a directional coupled waveguide I (16) of the first-stage directional coupling structure (1), and the other end of the phase-shifting curved waveguide is connected to an input end of a directional coupled waveguide III (30) of the second-stage directional coupling structure (3). One end of the phase-shifting straight waveguide (22) is connected to an output end of a directional coupled waveguide II (17) of the first-stage directional coupling structure (1), and the other end of the phase-shifting straight waveguide (22) is connected to an input end of a directional coupled waveguide IV (31) of the second-stage directional coupling structure (3). The adjustable wide-spectrum wavelength-insensitive directional coupler achieves wide-spectrum wavelength-insensitivity, a wide spectrum of splitting-ratio adjustment and low loss, and is of a compact size for easy integration with other devices.

A variable wavelength filter includes: an input optical fiber; a diffraction grating that disperses input light from the input optical fiber; a variable mirror that has a reflective surface, wherein an angle of the reflective surface is adjustable, the variable mirror reflects the input light dispersed by the diffraction grating, the input light reflected by the variable mirror passes through a normal optical path, the input light that passes through the normal optical path has a wavelength band defined based on the angle of the reflective surface, and the defined wavelength band has a center wavelength corresponding to the angle of the reflective surface; an output optical fiber that outputs a portion of the input light that has passed through the normal optical path; and an optical detector disposed on a propagation path of the input light from the input optical fiber to the output optical fiber.

An adjustable wide-spectrum wavelength-insensitive directional coupler, comprising a substrate (100). A first-stage directional coupling structure (1), a phase-shifting structure (2), and a second-stage directional coupling structure (3) are sequentially connected and disposed on the substrate (100). The phase-shifting structure (2) comprises a phase-shifting curved waveguide, a phase-shifting straight waveguide (22), and a third modulation component (26), wherein the third modulation component (26) is disposed on the phase-shifting curved waveguide. One end of the phase-shifting curved waveguide is connected to an output end of a directional coupled waveguide I (16) of the first-stage directional coupling structure (1), and the other end of the phase-shifting curved waveguide is connected to an input end of a directional coupled waveguide III (30) of the second-stage directional coupling structure (3). One end of the phase-shifting straight waveguide (22) is connected to an output end of a directional coupled waveguide II (17) of the first-stage directional coupling structure (1), and the other end of the phase-shifting straight waveguide (22) is connected to an input end of a directional coupled waveguide IV (31) of the second-stage directional coupling structure (3). The adjustable wide-spectrum wavelength-insensitive directional coupler achieves wide-spectrum wavelength-insensitivity, a wide spectrum of splitting-ratio adjustment and low loss, and is of a compact size for easy integration with other devices.

A broadband polarization beam splitter/combiner based on a gradient waveguide directional coupler, comprises a gradient waveguide directional coupler, a beam combining end (1), a curved waveguide (5), a TE mode end (6) and a TM mode end (7). The coupler consists of a straight end gradient waveguide (2) and a serial end gradient waveguide (3). The trend of change of the gradient waveguide (2) is opposite to the gradient waveguide (3), and a gap is provided between the gradient waveguide (2) and the gradient waveguide (3). The beam combining end (1) is connected with one end of the gradient waveguide (2), the other end of the gradient waveguide (2) is connected with one end of the curved waveguide (5), the other end of the curved waveguide (5) is connected with the TE end (6), and the waveguide (3) is connected with the TM end (7).

An optical membrane switch device includes a first membrane layer, a second membrane layer, and a spacer layer. The first membrane layer includes a first surface and light input lines. The light input lines are disposed on the first surface. Each light input line is slantingly extended with first branch lines. The second membrane layer includes a second surface and light output lines. The light output lines are disposed on the second surface. Each light output line is slantingly extended with second branch lines. The second branch lines respectively extend to the corresponding first branch lines to form contact regions. The spacer layer is clamped between the first membrane layer and the second membrane layer and includes through holes respectively corresponding to the contact regions. The first and second branch lines corresponding to the through holes at least partially overlap each other and keep a preset interval from each other.

An optical membrane switch device includes a first membrane layer, a second membrane layer, and a spacer layer. The first membrane layer includes a first surface and light input lines. The light input lines are disposed on the first surface. Each light input line is slantingly extended with first branch lines. The second membrane layer includes a second surface and light output lines. The light output lines are disposed on the second surface. Each light output line is slantingly extended with second branch lines. The second branch lines respectively extend to the corresponding first branch lines to form contact regions. The spacer layer is clamped between the first membrane layer and the second membrane layer and includes through holes respectively corresponding to the contact regions. The first and second branch lines corresponding to the through holes at least partially overlap each other and keep a preset interval from each other.

Various embodiments relate to polarization splitters. A polarization splitter may include a silicon nitride (SiN) waveguide core configured to receive an input light signal having a first polarization mode and a second polarization mode. The polarization splitter may further include a silicon (Si) slot waveguide core disposed proximate the SiN waveguide core. The Si slot waveguide core may include a tapered portion at a first end configured to couple the first polarization mode to the Si slot waveguide.