A silicon photonic integrated chip and a wavelength division multiplexer that includes at least two polarization control structures and at least one polarization-independent Mach-Zehnder interferometer on a silicon substrate are provided. The polarization control structure includes two input ports and one output port. The Mach-Zehnder interferometer includes two input ports and one optical signal output port for outputting a multiplexed optical signal. The output ports of the polarization control structures are connected to the input ports of the Mach-Zehnder interferometer. The polarization control structures have large bandwidths for increasing an optical bandwidth of the wavelength division multiplexer and reducing an optical loss. A quantity of phase shift arms that require tuning feedback is reduced to lower overall power consumption of the wavelength division multiplexer. Reliability and yields of the wavelength division multiplexer are enhanced due to a large manufacturing tolerance and good stability of the polarization control structures.

An integrally formed coupling module is provided. In the module, a total internal reflective surface reflects a first optical signal emitted by a laser to form a second optical signal, the second optical signal is output to the medium air interface, a medium air interface refracts the second optical signal to form a third optical signal, the third optical signal is output from air to the air medium interface, an air medium interface refracts the third optical signal to form a fourth optical signal, and then the fourth optical signal is output to an optical fiber. In addition, a refractive angle at which the medium air interface performs refraction to form the third optical signal is equal to an incidence angle at which the third optical signal is output to the air medium interface, and a first incident surface and a second incident surface are mutually perpendicular in space.

A photonic device such as a polarization controller includes a coupler, such as a 22 MMI coupler, or a series of such couplers. Couplers may be interspersed with other components such as phase shifters. Photodetectors such as photodiodes are coupled to input and output lines of the coupler or couplers, for example via taps. In various embodiments, all of the couplers include photodetectors monitoring light power for at least two of their inputs and outputs, and at least one of the couplers includes photodetectors monitoring at least three of its inputs and outputs. The arrangement of photodetectors can provide sufficient information for feedback control of the photonic device and/or determining the state of polarization of light within the photonic device. Signals from some photodetectors can be used to estimate light power at locations in the photonic device lacking photodetectors.

A pin hole or aperture is located or formed adjacent to the end surface of one or more of the input ports or fibers, or adjacent to one or more of the output ports or fibers, of a fiberoptic component. The aperture allows light to enter (or exit) the core of the associated fiber, and the non-transparent layer that surrounds the aperture blocks light from entering or exiting the cladding layer of the associated fiber. This blocking of the evanescent field in the cladding layer serves to reduce the polarization, wavelength, and temperature dependencies of the light coupling to the output port(s) or fiber(s) of the optical component. It can also reduce the passband width of the selected wavelength in tunable optical filter applications. The non-transparent layer surrounding the aperture can be made reflective, and light that is reflected by the non-transparent layer can be used for optical power monitoring.

A multi-stage interferometer circuit of the present invention includes: a multiplexing port; (N-1) stages of lattice type two-beam interferometers, wherein each stage includes a two-beam delay circuit having a path length difference of an integral multiple of M.Math. L/2, and wherein the two-beam delay circuit of the lattice type two-beam interferometer of the first stage is connected to the multiplexing port; an M-beam interferometer including: two sets of 1(M/2) optical couplers connected to the first optical coupler of the lattice type two-beam interferometer at the final stage; an M-array delay circuit, each delay circuit of which has a delay length different from each other by L; and MM optical couplers; and M demultiplexing ports, wherein one or more transversal filters are arranged inside the multi-stage interferometer circuit so that the light guided between the demultiplexing port and the multiplexing ports passes therethrough at least once.

An integrated polarization splitter and rotator (PSR) employs the TE0 and TE1 modes of propagating light, rather than the TE0 and TM0 modes used in conventional prior art PSR. The integrated PSR exhibits appreciably flatter wavelength response because it does not require a directional coupler to de-multiplex incoming polarizations. The PSR allows tuning of the TM0 loss to reduce polarization dependent loss (PDL). This integrated polarization splitter and rotator is applicable to all integrated platforms including Silicon-on-Insulator (SOI) and III-V semiconductor compound systems. The PSR may be very compact (122 m.sup.2), and provides low loss (<0.3 dB across the C-band) and ultra-broadband operation. The PSR also affords better control of polarization dependent losses.

A bidirectional optical transmission apparatus includes a first optical waveguide device, a second optical waveguide device, and a polarization-maintaining optical fiber that connects the first optical waveguide device and the second optical waveguide device. A direction of a slow axis of the polarization-maintaining optical fiber with respect to a first substrate at a connecting portion between the first optical waveguide device and the polarization-maintaining optical fiber and a direction of the slow axis of the polarization-maintaining optical fiber with respect to the second substrate at a connecting portion between the second optical waveguide device and the polarization-maintaining optical fiber are substantially orthogonal to each other.

An optical modulator module includes: a semiconductor modulator that includes a plurality of output waveguides; a first cylindrical lens that has a longitudinal direction in a direction in which the plurality of output waveguides are aligned, and through which lights output from the plurality of output waveguides penetrate; and a plurality of second cylindrical lenses each having a longitudinal direction that intersects with the longitudinal direction of the first cylindrical lens and allowing a corresponding light of the lights output from the plurality of output waveguides to penetrate therethrough.

An electro-optic combiner includes a polarization splitter and rotator (PSR) that directs a portion of incoming light having a first polarization through a first optical waveguide (OW). The PSR rotates a portion of the incoming light having a second polarization to the first polarization to provide polarization-rotated light. The PSR directs the polarization-rotated light through a second OW. Each of the first and second OW's has a respective combiner section. The first and second OW combiner sections extend parallel to each other and have opposite light propagation directions. A plurality of ring resonators is disposed between the combiner sections of the first and second OW's and within an evanescent optically coupling distance of both the first and second OW's. Each of ring resonators operates at a respective resonant wavelength to optically couple light from the combiner section of the first OW into the combiner section of the second OW.

A device has first, second and third elements fabricated on a common substrate. The first element supports a first optical mode in an active waveguide structure characterized by a mesa. The second element supports a second optical mode in a passive waveguide structure. The third element, at least partly butt-coupled to the first element, supports an intermediate optical mode in an intermediate waveguide structure characterized by a waveguide core cross section including a shallow step. A tapered waveguide structure in at least one of the second and third elements facilitates efficient adiabatic transformation between the second optical mode and the intermediate optical mode. No adiabatic transformation occurs between the intermediate optical mode and the first optical mode. Lithographic alignment marks facilitate precise alignment of the three elements during device fabrication.