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.

An optical device may include a waveguide-based Mach-Zehnder (MZ) interferometer associated with performing polarization multiplexing or demultiplexing. The waveguide-based MZ interferomenter may include a first MZ arm, a second MZ arm, and a set of stress-balancing trenches. A portion of the first MZ arm may be between at least two stress-reducing trenches of a plurality of stress-reducing trenches. The plurality of stress-reducing trenches may be in a cladding layer on a substrate. The set of stress-balancing trenches may be on an opposite side of the second MZ arm from the plurality of stress-reducing trenches. The set of stress-balancing trenches may be in the cladding layer on the substrate.

An optical module includes: an output section that outputs TM light; and a substrate-type optical waveguide. The substrate-type optical waveguide includes: a waveguide that guides the TM light outputted from the output section; a polarization rotating element that converts the TM light guided through the waveguide into TE light; and a function element that receives the TE light. In the optical module equation (aL)>(bL+c) is satisfies, where L is a length of the waveguide, a is a propagation loss of the TE light per unit length of the waveguide, b is a propagation loss of the TM light per unit length of the waveguide, and c is an insertion loss by the polarization rotating element.

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.

An apparatus of polarization self-compensated delay line interferometer. The apparatus includes a first waveguide arm of a first material of a first length disposed between an input coupler and an output coupler and a second waveguide arm of the first material of a second length different from the first length disposed between the same input coupler and the same output coupler. The apparatus produces an interference spectrum with multiple periodic passband peaks where certain TE (transverse electric) and TM (transverse magnetic) polarization mode passband peaks are lined up. The apparatus further includes a section of waveguide of a birefringence material of a third length added to the second waveguide arm to induce a phase shift of the lined-up TE/TM passband peaks to a designated grid as corresponding polarization compensated channels of a wide optical band.

A wavelength-division multiplexed (WDM) polarization-independent transmissive modulator (PITM) that receives a multi-wavelength continuous wave (CW) light of indeterminate polarization, splits the multi-wavelength CW light into two transverse electric (TE) polarized components, demultiplexer the polarized components into single-wavelength CW lights, modulates the single-wavelength CW lights using four-port cross-state or bypass-state modulators, multiplexes the modulated output of the four-port modulators (FPM) into two polarized modulated components, and combines the two polarized modulated components into a multi-wavelength modulated output signal.

A solid-state optical amplifier chip is described, with improved pumping, in which pump light from one or more solid-state light sources is coupled efficiently into the doped areas of the chip, resulting in amplification of an optical signal. The optical signal is carried in the core of an optical waveguide. Rare-earth elements are used as dopants, primarily in the cladding of the optical signal's waveguide core, in order to provide amplification of the optical signal through stimulated emission. A variety of waveguide structures are described for routing and distributing the pump light to the doped areas of the chip.

A depolarizer for a broadband optical source to split the source beam by power, not by polarization state, and route the components into respective light paths. A polarization rotator arranged in one of the light paths rotates the polarization state of that beam component to make it orthogonal to that of the other. The components are then recombined by a combiner and output. A variable optical attenuator is arranged in one of the light paths, which during operation is adjusted by a controller to maintain power equalization between the light paths and hence depolarization performance. The controller receives power measurements from the light paths and from after the combiner via respective sensors. With this feedforward design reminiscent of a Mach-Zehnder interferometer the light from a light source which generates highly polarized light can be depolarized in theory with zero insertion loss and in practice with losses of about 1 dB.

A solid-state optical amplifier chip is described, with improved pumping, in which pump light from one or more solid-state light sources is coupled efficiently into the doped areas of the chip, resulting in amplification of an optical signal. The optical signal is carried in the core of an optical waveguide. Rare-earth elements are used as dopants, primarily in the cladding of the optical signal's waveguide core, in order to provide amplification of the optical signal through stimulated emission. A variety of waveguide structures are described for routing and distributing the pump light to the doped areas of the chip.

To realize additional improvement and stabilization of optical characteristics, miniaturization, and low cost in an integration-type optical modulation device that includes a plurality of optical modulation elements, combines two modulated and linearly polarized light beams emitted from each of the modulation elements into one light beam. The optical modulation device includes two optical modulation elements (120a and 120b) each of which outputs two linearly polarized light beams; and four lenses (140a and the like) which respectively receive four linearly polarized light beams output from the two optical modulation elements. A distance between the two linearly polarized light beams which are output from one of the optical modulation elements and respectively pass through two of the lenses, and the two linearly polarized light beams which are output from the other optical modulation element and respectively pass through two of the lenses is set to gradually increase along a propagation direction.