An optical apparatus for compensating a measurement inaccuracy of polarization dependent loss (PDL) is described. The apparatus comprises a first polarization rotator splitter (PRS) for splitting an input beam into orthogonally polarized X and Y component beams and rotating one of the X and Y component beams to be in the same polarization as the other component beam; first and second circuits for processing the X and Y component beams respectively; a first polarization rotator combiner (PRC) for combining the X and Y component beams processed respectively by the first and second circuits into an output beam, one of the X and Y component beams being rotated to be orthogonally polarized with respect to the other component beam. The apparatus further comprises a first set of photodetectors for monitoring a first relative power between the X and Y component beams before the first and second circuits; a second set of photodetectors for monitoring a second relative power between the X and Y component beams processed respectively by the first and second circuits; and complementary PRSs and PRCs coupled between the first and second circuits and the second set of photo-detectors for compensating a measurement inaccuracy of PDL caused by the first PRS and PRC.

A 2-dimensional grating generates multi-mode light from two or more single-mode inputs. One or more waveguides couple the light from the single-mode inputs to the 2-dimensional grating. The 2-dimensional grating couples and transmits the generated multi-mode light to an optical fiber configured to support multiple modes.

A phase retarder and an optical comb filter are disclosed. The phase retarder includes a polarization beam splitter, a first air arm, and a second air arm, where the polarization beam splitter is configured to decompose a beam into a first light component propagated in a first direction and a second light component propagated in a second direction, the first direction is perpendicular to the second direction; the first air arm is disposed on a second side wall of the polarization beam splitter, and is configured to receive the first light component and reflect it back; and the second air arm is disposed on a third side wall of the polarization beam splitter, and is configured to receive the second light component and reflect it back. Two light components interfere, and the interference light is emitted from a fourth side wall of the polarization beam splitter.

A state of polarization (SOP) controller allows a randomly polarized input beam to be converted to a single linear polarization, while transferring substantially all of the power to the output. The input beam is split into orthogonal components and one of the components rotated and a phase difference between the components compensated for. The phase aligned components may then be recombined into a single output. The phase shifters may be reset during a reset period during which the impact on data transmission is reduced.

The various presented herein relate to an on-chip polarization beam splitter (PBS), which is adiabatic for the transverse magnetic (TM) mode and diabatic for the transverse electric (TE) mode. The PBS comprises a through waveguide and a cross waveguide, wherein an electromagnetic beam comprising TE mode and TM mode components is applied to an input port of the through waveguide. The PBS can be utilized to separate the TE mode component from the TM mode component, wherein the TE mode component exits the PBS via an output port of the through waveguide, and the TM mode component exits the PBS via an output port of the cross waveguide. The PBS has a structure that is tolerant to manufacturing variations and exhibits high polarization extinction ratios over a wide bandwidth.

A wavelength converter includes a polarization beam splitter configured to separate input light into a first polarization and a second polarization that are orthogonal to each other a non-linear optical medium configured to include a first incident end on which the first polarization separated by the polarization beam splitter is incident and a second incident end on which the second polarization separated by the polarization beam splitter is incident at a position different from a position of the first incident end, an optical multiplexer configured to multiplex the first polarization that has passed through the non-linear optical medium and the second polarization that has passed through the non-linear optical medium, and an optical element arranged between the non-linear optical medium and the optical multiplexer, and configured to correct a polarization axis of at least one of the first polarization and the second polarization incident on the optical multiplexer.

An electro-optic receiver includes a polarization splitter and rotator (PSR) that directs incoming light having a first polarization through a first end of an optical waveguide, and that rotates incoming light from a second polarization to the first polarization to create polarization-rotated light that is directed to a second end of the optical waveguide. The incoming light of the first polarization and the polarization-rotated light travel through the optical waveguide in opposite directions. A plurality of ring resonators is optically coupled the optical waveguide. Each ring resonator is configured to operate at a respective resonant wavelength, such that the incoming light of the first polarization having the respective resonant wavelength optically couples into said ring resonator in a first propagation direction, and such that the polarization-rotated light having the respective resonant wavelength optically couples into said ring resonator in a second propagation direction opposite the first propagation direction.

An optical transmitter (and methods of transmitting and receiving) includes a delay and modulation circuit configured to receive at least one optical beam and a first data signal (persistent data) and generate at least two or more modulated optical beams having the first data encoded therein. One of the modulated optical beams is a time-delayed or time-shifted version of another one of the modulated optical beams, and both beams are directed toward a target. The amount or time delay between the first and second optical beams can be modulated according to a second data signal (non-persistent data) to encode the second data therein. An optical receiver is configured to detect the two modulated optical beams and recover the first data. Because changes in the amount or time delays between the first and second optical beams results in a positional change in the location of the combined centroid of the received beams at a detector of the receiver, the second data can be recovered by detecting the positional changes.

Systems and methods for an integrated photonics vertical coupler are provided herein. In certain embodiments, a device includes a first waveguide having a first photon and a second photon propagating therein, wherein the first photon and the second photon are propagating in orthogonal modes. Further, the device includes a second waveguide having a second coupling portion in close proximity with a first coupling portion of the first waveguide, wherein a physical relationship between the first waveguide and the second waveguide along the length of the second coupling portion causes an adiabatic transfer of the first photon and the second photon into distinct orthogonal modes of the second waveguide at different locations in the second coupling portion.

A phase decoding method and apparatus for quantum key distribution based on reflection with an orthogonal rotation of polarization, and a corresponding system. The method comprises: splitting an input optical pulse of an arbitrary polarization state into two optical pulses by a beam splitter; and, transmitting the two optical pulses respectively along two optical paths, with a relative time delay applied to them, and then reflecting them back to the beam splitter respectively by two reflecting devices to be combined and output by the beam splitter. A phase modulation is performed on at least one of the two optical pulses according to a quantum key distribution protocol, and two orthogonal polarization states of the optical pulse are reflected with an orthogonal rotation of polarization, so that each orthogonal polarization state of the optical pulse, after being reflected by the corresponding reflecting device, is transformed to a polarization state orthogonal thereto.