An optical switch (10) comprising: inputs (12) to receive input optical signals at respective wavelengths and having planar wavefronts; conversion apparatus (14) to convert each input optical signal into a respective optical signal having a respective helical wavefront, each helical wavefront having a different orbital angular momentum, OAM; optical multiplexing apparatus (16) to receive each helical wavefront optical signal from the conversion apparatus and to multiplex the helical wavefront optical signals into an OAM multiplexed optical signal; and optical demultiplexing apparatus (18) comprising a plurality of outputs (20), the optical demultiplexing apparatus arranged to: receive the OAM multiplexed optical signal; demultiplex the OAM multiplexed optical signal into a plurality of wavelength multiplexed optical signals each having a different OAM; reconvert each wavelength multiplexed optical signal from its helical wavefront into a respective planar wavefront; and deliver each planar wavefront wavelength multiplexed optical signal to a respective one of the outputs according to the respective OAM it had before reconversion.

An optical device (501) is disclosed, including a spatial multiplexer/demultiplexer (520) and an optical splitter (510). The optical splitter (510) is an M:N optical splitter, M is greater than or equal to 2, and N is greater than or equal to M. M is a quantity of common ports of the optical splitter (510), and N is a quantity of drop ports of the optical splitter (510). The spatial multiplexer/demultiplexer (520) includes one common port (521) and M drop ports (522-1 to 522-M). The M drop ports of the spatial multiplexer/demultiplexer (520) are connected to the M common ports of the optical splitter (510). The common port (521) of the spatial multiplexer/demultiplexer (520) has a capability of transmitting optical signals in multiple spatial modes.

Aspects of the disclosure relate to wireless communication including mode division multiplexing of data and reference signals using different orbital angular momentum (OAM) modes. An OAM transmitter may transmit a reference signal (RS) configuration information to an OAM receiver that indicates radio resources for a plurality of OAM modes. The OAM transmitter may further transmit data on a first OAM mode of the plurality of OAM modes using first radio resources of the radio resources indicated by the RS configuration information. The OAM transmitter may further transmit a reference signal on a second OAM mode of the plurality of OAM modes using the first radio resources of the radio resources indicated by the RS configuration information. The OAM receiver may receive the data on the first OAM mode and the reference signal on the second OAM mode. Other aspects, embodiments, and features are also claimed and described.

Aspects of this technical solution are directed to multiplexed transmission by optical beam transmission. A method can include generating a first beam having a first frequency in an optical frequency range, generating a second beam including data and having a second frequency in the optical frequency range, converting the first beam and the second beam into a third beam including the data and having a third frequency based on a difference between the first frequency and the second frequency, and transforming the third beam into a fourth beam having a first angular distribution and including a first portion of the data, and into a fifth beam having a second angular distribution corresponding to the first angular distribution and including a second portion of the data.

A communication method based on orbital angular momentum (OAM) is performed by a receiving end, and includes: transmitting indication information to indicate a transmitting end to determine a transmitting mode. Transmitting indication information may include determining a target OAM mode combination from preset K+1 OAM mode combinations and transmitting the indication information to indicate to determine the transmitting mode of the transmitting end based on the target OAM mode combination. It may also include one of determining channel information about a wireless channel between the receiving end and the transmitting end; and transmitting second indication information, or determining a first deflection angle between the receiving end and the transmitting end; and transmitting third indication information.

A method for transmitting an orthogonal function processed signal over a communications link on a fiber involves generating at least one mode crosstalk matrix illustrating mode crosstalk between transmitted modes and adjacent modes within the fiber. Adjacent modes to be multiplexed together are selected based on entries within the generated mode crosstalk matrix being less than or equal to a predetermined value. The transmitted modes and the selected adjacent modes are multiplexed together into the orthogonal function processed signal for transmission on the communications link on the fiber.

A system for enabling signal penetration into a building includes first circuitry, located on an outside of the building, that receives millimeter wave signals and converting the millimeter wave signals into a format that penetrates into an interior of a building for reception by wireless devices within the building. Second circuitry, located on an inside of the building and communicatively linked with the first circuitry, receives the millimeter wave signals in the format that penetrates into an interior of the building and converts the millimeter wave signals in the format to a second format for transmission to the wireless devices within the building.

A method for transmitting shared channel based on orbital angular momentum includes: a network device determining, based on the current channel information, a target OAM mode for transmitting a shared channel, and transmitting a shared channel according to the target OAM mode.

An optical integrated light source includes a plurality of topological ring resonators. Each of the topological ring resonators is defined by an interface between two distinct periodic structures having different topological invariants such that a one-way edge mode may be excited along the interface. A magnetic material is arranged to interact with the plurality of topological ring resonators such that the optical integrated light source is structured and configured to generate plural beams each carrying large orbital angular momentum.

A communications system has a transmitter circuit for transmitting a communications signal. The transmitter receives a plurality of input data streams and applies an orthogonal function to each of the plurality of input data streams. The transmitter groups the input streams having the orthogonal function applied thereto into a plurality of groups. The orthogonal functions applied to the plurality of input data streams do not repeat within the plurality of groups to limit interference between the input data streams within the group. The transmitter applies a different wavelength to each of the plurality of groups input data streams. The different wavelengths limit interference between the plurality of groups of input data streams. The transmitter applies a positive polarization and a negative polarization to each of the plurality of groups of input data having a different wavelength applied thereto. The positive and the negative polarizations are applied to a pair of groups having a same wavelength applied thereto limit interference between the pair of groups. The transmitter transmits the plurality of input of data streams over a plurality of channels on a communications link as the communications signal. Each of the plurality of channels has a unique combination of orthogonal function, wavelength and polarization associated therewith.