The present invention provides a Point-Symmetric Mach-Zehnder-Interferometer (PSMZI) device, comprising three consecutive path delay sections (PDSs) provided as two outer PDS and one center PDS, each PDS including an upper waveguide arm and a lower waveguide arm. The PSMZI device also includes four asymmetric couplers (ACs) each AC including an upper waveguide portion and a lower waveguide portion. One AC is arranged directly on each side of each PDS, the upper and lower waveguide portions being respectively coupled to the upper and lower waveguide arms. Further, the AC on the one side of the PDS is point-symmetric to the AC on the other side of the PDS, and the two ACs and the one outer PDS arranged on the one side of the center PDS are together point-symmetric to the two ACs and the one outer PDS arranged on the other side of the center PDS.

A tunable transmission optical filter is optically coupled between a laser section and semiconductor optical amplifier (SOA) section of a tunable laser device. The optical filter may be tuned to provide a high transmission near the lasing peak while suppressing a significant portion of back-propagating amplified spontaneous emission (ASE) of the SOA section. Without the optical filter, the laser output spectrum may develop side lobes of higher intensity after the ASE is amplified and reflected in the forward direction by the laser gain and mirror sections. While lessening the side lobes, the optical filter simultaneously transmits the laser peak for amplification by the SOA section.

An optical modulation device configured of a planar optical waveguide, includes: a light incidence unit which allows light to be incident on the planar optical waveguide; a Mach-Zehnder interferometer which includes a first optical splitter section branching the light incident on the light incidence unit, two arm portions guiding the light branched by the first optical splitter section, a phase modulation unit linearly disposed on each of the two arm portions, and a first optical coupler section combining the light guided from the two arm portions; a light launching unit which launches the light combined by the first optical coupler section from the planar optical waveguide; and a traveling-wave electrode which includes an input unit and an output unit, and applies a voltage to the phase modulation unit.

A wavelength division multiplexing filter comprises: a first multi-order Mach-Zehnder interferometer comprising a plurality of first-order Mach-Zehnder interferometers, and a second multi-order Mach-Zehnder interferometer comprising a plurality of first-order Mach-Zehnder interferometers; wherein the first multi-order Mach-Zehnder interferometer and the second multi-order Mach-Zehnder interferometer are included in a group of multiple multi-order Mach-Zehnder interferometers arranged within a binary tree arrangement, the binary tree arrangement comprising: a first set of a plurality of multi-order Mach-Zehnder interferometers, the first set including the first multi-order Mach-Zehnder interferometer, and having an associated spectral response with a first spacing between adjacent passbands, and a second set of at least twice as many multi-order Mach-Zehnder interferometers as in the first set, the second set including the second multi-order Mach-Zehnder interferometer, and having an associated spectral response with a second spacing between adjacent passbands that is twice the first spacing.

A wavelength demultiplexer includes a photonic circuit and a control circuit that adjusts wavelength characteristics of the photonic circuit. The photonic circuit converts two orthogonal polarized waves contained in the incident light into two same polarized waves, which are supplied to a first optical demultiplexing circuit and a second optical demultiplexing circuit provided in the photonic circuit and having the same configuration. The photonic circuit supplies a total output power of monitor lights extracted from the same positions in the first optical demultiplexing circuit and the second optical demultiplexing circuit to the control circuit. The control circuit controls a first wavelength characteristic of the first optical demultiplexing circuit and a second wavelength characteristic of the second optical demultiplexing circuit based on the total output power of the monitor lights.

The present invention discloses a directional photonic coupler (1) with independent tuning of the coupling factor and phase difference. The coupler comprises: two waveguides (4, 5), with respective propagation constants “β.sub.1, β.sub.2”, on which phase shifters (6, 7) configured to modify the propagation coefficients are located. Both phase shifters are configured such that, by independent modification (differential or unique) of the propagation coefficients, the power coupling factor (K) between an input signal (2a or 2b) and the output signals (3b and 3a) is tuned, and by equal and simultaneous modification of the propagation coefficients, the common phase difference of the optical output signals (3 a, 3b) is tuned. A third phase shifter (15) can be used to retune the phase difference at the input/output of one of the waveguides. The coupler is of particular interest in PIC circuits, coupled resonators, Mach-Zehnder interferometers and mesh structures.

A nested Mach-Zehnder device may comprise a parent pre-stage interferometer, a parent interferometer coupled to the parent pre-stage interferometer, a first child pre-stage interferometer, a first child interferometer coupled to the first child pre-stage interferometer, a second child pre-stage interferometer, a second child interferometer coupled to the second child pre-stage interferometer, wherein a phase of each interferometer is electrically adjustable. The nested Mach-Zehnder device may comprise one or more components to: determine a performance parameter associated with a constellation diagram generated by the nested Mach-Zehnder device; determine that the performance parameter does not satisfy a threshold, and cause a phase of at least one pre-stage interferometer, of the parent pre-stage interferometer, the first child pre-stage interferometer, or the second child pre-stage interferometer, to be electrically adjusted to cause the performance parameter to satisfy the threshold.

Methods for design and production of highly sensitive active and passive light detecting devices and systems. Orders of magnitude improvement in optical signal detection is made possible in high noise or low contrast scenes. The current invention creates a small spectral difference between two parts of a split light stream. When recombined, the altered light streams partially correlate, and that generates full amplitude signal oscillation at a frequency that depends on the constituent spectrum. The full amplitude signals and spectrum dependent oscillation make signal discrimination much better than intensity-only methods. The effect of read noise, amplifier noise, dark current noise, and thermal noise due to photo detector shunt resistance, become less important when compared to light detection using prior art methods

A multi-path interference filter. The multi-path interference filter includes a first port waveguide, a second port waveguide, and an optical structure connecting the first port waveguide and the second port waveguide. The optical structure has a first optical path from the first port waveguide to the second port waveguide, and a second optical path, different from the first optical path, from the first port waveguide to the second port waveguide. The first optical path has a portion, having a first length, within hydrogenated amorphous silicon. The second optical path has a portion, having a second length, within crystalline silicon, and the second optical path has either no portion within hydrogenated amorphous silicon, or a portion, having a third length, within hydrogenated amorphous silicon, the third length being less than the first length.

A tunable optical filter includes sequentially coupled Mach-Zehnder (MZ) interferometers. The first and last interferometers are configured to function as variable power splitter/combiner, whereas the middle interferometer or interferometers have unequal optical paths, creating a desired spectral response of the entire filter. The amplitude of the spectral response can be varied by varying the optical power splitting/combining ratios.