A system for enabling signal penetration into a building includes a transceiver located on an exterior of the building for receiving signals at a first frequency transmitted from a source outside of the building. An optical bridge receives the signals at the first frequency that experiences losses when penetrating an exterior surface of the building, converts the received signals at the first frequency into a first format that overcome losses caused by penetrating an exterior surface of the building and transmits the signals through the exterior surface of the building. A WiFi transceiver located on the interior of the building and connected to the optical bridge converts between the signals in the first format and WiFi signals and for transmitting the WiFi signals to the interior of the building and receiving the WiFi signals from the interior of the building.

A telecommunication system is based on spatial multiplexing of optical cables and uses optical space connected modulation (OSCM) to establish optical telecommunication links, where multiple optical communication channels are established with a single optical system. The system comprises: An OSCM transmitter system (1), a communication channel (11), and an OSCM receiver system (2). The OSCM transmitter system (1) includes a data input port (3), an OSCM modulator system (4), a generic light source (8), and an optical transmitter system (10). The OSCM modulator system (4) includes a processor system (5), and a spatial modulator (7). The OSCM receiver system (2) includes an optical receiver system (12), and an OSCM demodulator system (14). The OSCM demodulator system (14) includes an image sensor (13) and a processor system (15). The system allows multiple transmission channels to be formed using a single optical system.

A communications system includes transmitter circuit for receiving a plurality of input data streams and applying a different orthogonal function to each of the plurality of input data streams. The transmitter circuit processes each of the plurality of input data streams having the different orthogonal function applied thereto to spatially locate a first group of the plurality of input data streams having the different orthogonal function applied thereto onto a first carrier signal and to spatially locate a second group of the plurality of input data streams having the different orthogonal function applied thereto onto a second carrier signal. The transmitter circuit temporally locates the first carrier signal and the second carrier signal onto a third carrier signal and transmits the third carrier signal over a communications link. A receiver circuit receives the third carrier signal over the communications link and separates in time the third carrier signal into the first carrier signal and the second carrier signal. The receiver then separates the plurality of input data streams having the different orthogonal function applied thereto into the plurality of input data streams each having the different orthogonal function applied thereto. Finally, the receiver removes the orthogonal function from each of the plurality of input data streams and outputs the plurality of input data streams.

An interference component generated because a plurality of carrier generation units and a plurality of local oscillation units are asynchronous is used as state information, a predetermined state equation for calculating posterior state information on the basis of prior state information, and a transmission data sequence are used as observation information, a Kalman filter algorithm is applied to a predetermined observation equation for calculating the observation information in a state indicated by the posterior state information on the basis of the posterior state information calculated by the state equation, a reception data sequence, and a weight matrix to calculate a posterior state estimate of the interference component, and an estimated sequence of the transmission data sequence from which the interference component has been removed is calculated on the basis of the calculated posterior state estimate.

A free space optical communication device includes: a plurality of light transmitting/receiving sections; and at least one processor configured to execute: a communication control process of controlling communication which is to be carried out via the plurality of light transmitting/receiving sections, in the communication control process, the at least one processor (a) determining a required communication capacity for the communication and (b) controlling, on the basis of the required communication capacity, the number of light transmitting/receiving sections to be used for the communication.

An embodiment mixes classical and quantum signals in the same transmission such that an eavesdropper can be detected using the quantum signals while maintaining high classical transmission rates. The embodiment uses security enhancement from quantum signals while maintaining the high data rates of classical communication. The eavesdropper introduces noise when trying to collect information on the physical layer. This noise can be observed by monitoring the quantum signals.

To provide a free space optical communication apparatus with an increased efficiency of optical axis alignment. A free space optical communication apparatus (1) includes: light transmitting sections (10); and an optical axis alignment section (20) configured to align an optical axis of each of the light transmitting sections (10) with a corresponding one of light receiving sections (130) included in a communication target. The optical axis alignment section (20) causes at least one of the light transmitting sections (10) to emit scan light (3) while varying an emitting direction, and aligns an optical axis of a light transmitting section (10) which is other than the at least one light transmitting section (10), based on an emitting direction of the scan light (3) emitted from the at least one light transmitting section (10) and received by a corresponding one of the light receiving sections (130).

An optical signal transmitting device comprises an optical transmitter and a mode converter. The optical transmitter transmits a multi-path transmitted initial optical signal to the mode converter, wherein the initial optical signal comprises a first optical signal and a second optical signal both having a first wavelength, and a third optical signal having a second wavelength different from first wavelength. The mode converter is configured to perform phase conversion on the incident initial optical signal to obtain and reflect a first target optical signal, which is single-path transmitted and comprises the third optical signal, the first optical signal transmitted in a first mode, and the second optical signal transmitted in a second mode different from the first mode.

In order to estimate an upper limit value of a bit error rate in an optical transmission unit for an optical transmission system in which an optical sender and an optical receiver are connected each other through the optical transmission unit that utilizes plural spatial resources, and coherent detection is used, after obtaining an amplitude of each crosstalk for different spatial resource in the optical transmission unit and variance of additive white Gaussian noise in the optical transmission system, by changing a value of an independent variable in a formula of the bit error rate, a minimum value of the formula is searched for as the upper limit value of the bit error rate. The formula is represented by the amplitude of each crosstalk, the variance of the additive white Gaussian noise and the independent variable that is different from a time axis.

The present invention relates to a method and a device for dual-polarisation, fiber-optic SDM transmission. The transmission method uses specific I/Q coding that makes it possible to combat the effects of PDL. The modulation symbols to be transmitted on the 2N polarisation states of the N basic spatial channels are broken down into real and imaginary values (220). A real vector composed by concatenating these real values and imaginary values is then constructed. A first invertible linear transformation, represented by a dense real matrix, is applied (230) to the resulting real vector to provide a transformed real vector. Complex transmission symbols are formed by I/Q combination (240) of the components of the transformed vector, the transmission symbols then modulating the different polarisation states of the basic spatial channels.