A bricked sub-wavelength periodic waveguide and a modal adapter, power divider and polarization splitter that use the waveguide. The waveguide includes blocks disposed periodically with a period L.sub.z on a substrate and which alternate with a covering material. The first blocks have a width a.sub.x and the second blocks have a width b.sub.x, alternating on the substrate according to a period L.sub.x the second blocks being shifted a distance d.sub.z the first blocks in the direction of propagation. A modal adapter, a power divider and a polarization splitter all use the periodic waveguide and can operate with larger wave periods without leaving the sub-wavelength regime.

A demultiplexer for use in a wavelength division multiplexed system. The demultiplexer comprises: an input waveguide, configured to receive a wavelength division multiplexed signal; a demultiplexing element, configured to demultiplex the multiplexed signal received from the input waveguide into a plurality of multi-mode demultiplexed signal components; a multi-mode output waveguide, the multi-mode output waveguide being coupled to the demultiplexing element and configured to receive one of the multi-mode demultiplexed signal components; and a splitter, coupled to the multi-mode output waveguide, and configured to split the received multi-mode demultiplexed signal component into two single-mode outputs.

An amplification optical fiber operable to propagate light beams in a plurality of modes in a predetermined wavelength range through a core doped with a rare earth element, wherein Expression (1) is satisfied, where a cutoff wavelength of a propagated highest mode light beam is defined as max, under conditions in which the cutoff wavelength of the highest mode light beam is defined as c, a shortest wavelength of the wavelength range is defined as min, and a cutoff wavelength of a second-highest mode light beam to the highest mode light beam is min.

c>0.5 min+0.5 max(1)

An embodiment of the invention relates to a BI-MMF with OH group concentrations controlled along a radial direction. In the BI-MMF, an OH group concentration distribution along the radial direction has a shape in which a concentration peak is located in a concentration control interval provided between an outer periphery of a core and a trench part, including an interface between the core and trench part.

In a multi-chip module and method, the multi-chip module includes a carrier; a multimode optical waveguide formed on and/or in the carrier; a first and second chip disposed on the carrier and coupled to the multimode optical waveguide; wherein the first chip is configured to transmit light beams into the multimode optical waveguide; the multimode optical waveguide is configured to generate mixed light beams that are an at least partial superposition of the light beams; the second chip is configured to receive the mixed light beams from the multimode optical waveguide; and the second chip is configured to store a representation of the received mixed light beams as a transmission signature and/or as a cryptographic key in a memory associated with the second chip, and/or compare the representation of the received mixed light beams with a target representation stored in the memory associated with the second chip.

An optical coupler includes a first waveguide including a first multi-mode waveguide section having a cross-section characterized by a first height and a first width that is greater than the first height and a second waveguide including a second multi-mode waveguide section having a cross-section characterized by a second height and a second width that is greater than the second height. The first multi-mode waveguide section is positioned adjacent to the second multi-mode waveguide section at least partially above or below the second multi-mode waveguide so that light entering the first multi-mode waveguide section is coupled from the first multi-mode waveguide section to the second multi-mode waveguide section. Methods for coupling light between waveguides with the optical coupler and optical devices that include the optical coupler are also described.

A device and method are provided. The device includes a bus waveguide having a longitudinal axis, a lower waveguide disposed on a first side of the bus waveguide, and an upper waveguide disposed on a second side of the bus waveguide opposite to the first side of the bus waveguide, wherein the upper waveguide substantially matches a path of the lower waveguide. The method includes receiving a TE.sub.1 mode optical signal on a bus waveguide, receiving a TE.sub.0 mode optical signal on a lower waveguide disposed below the bus waveguide, mode multiplexing the TE.sub.1 mode optical signal and the TE.sub.0 mode optical signal without converting the TE.sub.0 mode optical signal or the TE.sub.1 mode optical signal to another mode, and outputting the TE.sub.0 mode optical signal and the TE.sub.1 mode optical signal on the bus waveguide.

An integrated optical structure for multiplexing and/or demultiplexing an optical signal comprises a main waveguide having two parallel side surfaces, a first waveguide which meets the main waveguide at a first region on one of the two side surfaces, and a plurality of second waveguides which meet the main waveguide at a second region on one of the two side surfaces. The second region is spaced at a determined distance from the first region. The two side surfaces are arranged at a first angle relative to an extension direction of the first waveguide and a second angle relative to extension directions of the plurality of second waveguides. The optical structure further comprises one or more waveguide extension structures. Each waveguide extension structure is arranged adjacent to one of the two side surfaces of the main waveguide at a region that is different to the first and the second region.

A passive light wave conversion module for converting an incoming light wave having an undefined polarization into a light wave having a defined polarization, being one of Transverse Electric, TE, polarization or Transverse Magnetic, TM, polarization, the passive light wave conversion module comprising an optical splitter for splitting incoming light, two 50% input polarization converters for converting power in the incoming polarization for 50%, wherein the input polarization converters are connected to the optical splitter, at least one 50% output polarization converter for converting power in the polarizations for 50%, a bimodal phase shifter for introducing phase shifts between the TE polarization and the TM polarization, wherein the bimodal phase shifter is connected to the two 50% input polarization converters and the least one 50% output polarization converter.

A method for producing a planar light circuit is specified. The method comprises: providing a substrate free of light producing regions, depositing a waveguide layer, applying a photostructurable mask on the waveguide layer, photostructuring of the photostructurable mask such that the photostructurable mask is removed in regions, etching of the waveguide layer in the regions such that channels are produced in the waveguide layer, wherein the channels confine waveguides, removal of the photostructurable mask layer, and singulating into a planar light circuit. Furthermore, a planar light circuit is specified.