Joint estimation of the framer index and the frequency offset in an optical communication system are described among various other features. A transmitter can transmit data frames using pilot and framer symbols. A receiver can estimate the framer index and frequency offset using the pilot and framer symbols, and identify the beginning of a header portion of a data frame. By identifying the beginning of the header portion of a data frame, the receiver can then process data received from the transmitter in a manner synchronous to the manner in which the data was transmitted by the transmitter.

The present invention relates to a central office device, a remote site device, and a communication method thereof that can be used in a radio over fiber (RoF) technique. Provided are a central office device and a communication method thereof that convert an analog signal into a signal having a carrier with an intermediate frequency and converts the converted signal into a digital signal to transmit the converted digital signal to a remote site device. Provided are a remote site device and a communication method thereof that filter a digital signal having a carrier with an intermediate frequency to easily induce a corresponding analog signal.

An optical transmission system transmits a Radio Frequency (RF) signal by a frequency division multiplexing method. The optical transmission system includes a Transmitter Optical SubAssembly (TOSA), an optical fiber, and a Receiver Optical SubAssembly (ROSA). The TOSA includes a surface emitting laser diode configured to be capable of emitting light at output of 0.8 mW or more. In the optical transmission system including the surface emitting laser diode, a noise index obtained by a measurement method including a predetermined step is 10.0 dBμV or less.

A radio communication system for duplex communication comprising an optical carrier generator for generating optical carrier signals, a local oscillator (LO) for generating an electrical signal in a radio communication band, an information signal source, electro-optic modulators driven directly at an input electrical port by said information signal and said LO signal to modulate a portion of said optical carrier signal to form a modulated portion being an optical band information signal for transmission over an optical link; and a photodetector remote from said electro-optic modulators for receiving said transmitted optical band information signal from said optical link, and directly generating an electrical signal that is up-converted for radio transmission, or down-converted to a baseband frequency.

An optical/RF wireless hybrid communication system and a control method capable of solving the instability of link states of an RF wireless link and an optical wireless link is provided. According to an optical/RF wireless hybrid communication system and a control method of the present invention, when data is transmitted, the link is not limited to one of an RF wireless link and an optical wireless link, a link state is determined based on signal quality received in channels of both the RF wireless link and the optical wireless link, and a distribution of data to be transmitted in each link is determined based on a result thereof. For this reason, the link can be switched according to circumstances of the transmission state due to an external disturbance and the like.

An RF imaging receiver using photonic spatial beam processing is provided with an optical beam steerer that acts on the individual modulated optical signals to induce individual phase delays that produce a phase delay with a linear term, and possibly spherical or aspherical terms, across a two-dimensional wavefront of the composite optical signal to steer the composite optical signal and move the location of the spot on the optical detector array. The optical beam steerer may change the path length or a refractive index for each of the modulated optical signals to induce the requisite phase delays. The optical beam steerer may be implemented, for example, with a Risley prism or liquid crystal or MEMs spatial light modulator.

Joint estimation of the framer index and the frequency offset in an optical communication system are described among various other features. A transmitter can transmit data frames using pilot and framer symbols. A receiver can estimate the framer index and frequency offset using the pilot and framer symbols, and identify the beginning of a header portion of a data frame. By identifying the beginning of the header portion of a data frame, the receiver can synchronize, with less error, the data transmitted by the transmitter and the data it received. To further improve the framer index estimation, a lock indicator signal can be generated to signal to other receiver components that the estimated framer indices are reliable. The receiver can determine frequency offset and additional framer index estimations with increased reliability when performed after the lock indicator signal is generated.

High-performance ultra-wideband Phased Array Antennas (PAA) are disclosed, having unique capabilities, enabled through photonic integrated circuits and novel optical architectures. Unique capabilities for PAA systems are enabled by photonic integration and ultra-low-loss waveguides. Novel aspects include optical multiplexing combining wavelength division multiplexing and/or a novel extension to array photodetectors, providing the capability to combine many RF photonic signals with very low loss. Architectures include tunable optical up-conversion and down-conversion systems, moving a chosen frequency band between baseband and a high RF frequency band with high dynamic range. Simultaneous multi-channel RF beamforming is achieved through power combining/splitting of optical signals.

Grid of beams (GoB) adaptation in a wireless communications circuit, particularly for a wireless communications system (WCS), is disclosed. The wireless communications circuit may be provided in the WCS to provide radio frequency (RF) coverage in a wireless communications cell. In this regard, an antenna array is provided in the wireless communications circuit to radiate the GoB, which includes a number of RF beams corresponding to an RF communications signal(s), in the wireless communications cell. In examples discussed herein, the wireless communications circuit can be configured to detect a coverage condition change in the wireless communications cell and modify the GoB accordingly. By adapting the GoB to the coverage condition change, it may be possible to reduce processing overhead and improve resource usage, data throughput, and system adaptability of the wireless communications circuit, thus helping to optimize RF coverage in the wireless communications cell.

An optical and electrical hybrid beamforming transmitter, receiver, and signal processing method are provided. The transmitter includes, but is not limited to, two photoelectric converters, two adjusting circuits, and an antenna array. The photoelectric converter converts an optical signal into an initial electric signal, respectively. The adjusting circuit is coupled to the photoelectric converter, and are adapted for delaying the initial electric signal according to an expected beam pattern formed by the antenna array, respectively, to output an adjusted electric signal. The antenna array includes two antennas that are coupled to the adjusting circuit. The antenna radiates electromagnetic wave according to the adjusted electric signal. Accordingly, a phase of the signal may be adjusted, and the number of the elements may be reduced.