A radio frequency (RF) multiplexer includes, for example, a common port, a first port for a first frequency band, a second port for a second frequency band, and a third port for a third frequency band. The RF multiplexer also includes, for example, a first quadrature hybrid coupler (QHC), a second QHC and a third QHC. A coupling of the first QHC, a first pair of filters, and the second QHC separates the first frequency band and the second frequency band from the common port to the first port and to the second port, respectively. A coupling of the first QHC, a second pair of filters, and the third QHC separates the first frequency band and the third frequency band from the common port to the first port and to the third port respectively.

A radio frequency (RF) multiplexer includes, for example, a common port, a first port for a first frequency band, a second port for a second frequency band, and a third port for a third frequency band. The RF multiplexer also includes, for example, a first quadrature hybrid coupler (QHC), a second QHC and a third QHC. A coupling of the first QHC, a first pair of filters, and the second QHC separates the first frequency band and the second frequency band from the common port to the first port and to the second port, respectively. A coupling of the first QHC, a second pair of filters, and the third QHC separates the first frequency band and the third frequency band from the common port to the first port and to the third port respectively.

An optical communication network includes a downstream optical transceiver. The downstream optical transceiver includes at least one coherent optical transmitter configured to transmit a downstream coherent dual-band optical signal having a left-side band portion, a right-side band portion, and a central optical carrier disposed within a guard band between the left-side band portion and the right-side band portion. The network further includes an optical transport medium configured to carry the downstream coherent dual-band optical signal from the downstream optical transceiver. The network further includes at least one modem device operably coupled to the optical transport medium and configured to receive the downstream coherent dual-band optical signal from the optical transport medium. The at least one modem device includes a downstream coherent optical receiver, and a first slave laser injection locked to a frequency of the central optical carrier.

Length metrology apparatuses and methods are disclosed for measuring both specular and non-specular surfaces with high accuracy and precision, and with suppressed phase induced distance errors. In one embodiment, a system includes a laser source exhibiting a first and second laser outputs with optical frequencies that are modulated linearly over large frequency ranges. The system further includes calibration and signal processing portions configured to determine a calibrated distance to at least one sample.

A method (10) of bi-directional optical communication, the method comprising: generating (12) a first optical communication signal for transmission in one direction through an optical fibre, generating the first optical communication signal comprising: receiving information for transmission and generating (14) a baseband signal comprising a representation of the information; performing digital upconversion (16) of the baseband signal to form an upconverted baseband signal; performing optical modulation (18) of an optical carrier signal with the upconverted baseband signal; and restricting an optical spectrum of the first optical communication signal to a first portion of an optical channel frequency slot by performing one of digital filtering (16) in addition to digital upconversion and optical filtering (36) after optical modulation; and receiving (20) a second optical communication signal transmitted in an opposite direction through the optical fibre, the second optical communication signal having an optical spectrum occupying a second portion of the optical channel frequency slot, separate to the first portion.

A method for operating an optical demodulator includes receiving a double sideband suppressed carrier (DSBSC) optical signal. The method further includes passing the DSBSC optical signal through a Costas loop circuit. The method further includes outputting a radio frequency (RF) signal from a quadrature port of the Costas loop circuit.

Apparatus including an optical signal generator, a data transmission path, and an optical signal receiver. Optical signal generator includes a coherent light source for generating a spectrum of carrier signals at different carrier frequencies, an optical demultiplexer that receives and separates the different carrier signals into separate optical paths, a pair of optical modulators located in each of the separate optical paths to modulate each different carrier signal with a data signal and produce an upper and lower sideband pair at each of the different carrier frequencies, and an optical interleaver to combine the upper and lower sideband pairs into an optical super-channel of interleaved sub-bands. Optical signal receiver includes a demodulator for extracting the data signals. Optical modulators are configured to reuse each carrier signal to transmit different data in each of the upper sideband and the lower sideband and increase the capacity of the super-channel. Also a method.

It is possible to suppress carrier light with a simple configuration when modulating the carrier light to generate optical sideband components. An optical carrier-suppressed signal generator includes first splitting means used to split input carrier light into two light beams, an optical modulator which modulates one split carrier light beam and outputs light including optical sideband components, a phase modulator which phase-modulates another split carrier light beam, and second or third splitting means used to split the output light of the optical modulator into two light beams. The output light split by the second or third splitting means and the output light of the phase modulator are multiplexed to obtain the amplitude of the signal waveform of optical power, and the optical modulator is controlled such that the obtained value is minimized.

A radio frequency (RF) multiplexer includes, for example, a common port, a first port for a first frequency band, a second port for a second frequency band, and a third port for a third frequency band. The RF multiplexer also includes, for example, a first quadrature hybrid coupler (QHC), a second QHC and a third QHC. A coupling of the first QHC, a first pair of filters, and the second QHC separates the first frequency band and the second frequency band from the common port to the first port and to the second port, respectively. A coupling of the first QHC, a second pair of filters, and the third QHC separates the first frequency band and the third frequency band from the common port to the first port and to the third port respectively.

A radio frequency (RF) multiplexer includes, for example, a common port, a first port for a first frequency band, a second port for a second frequency band, and a third port for a third frequency band. The RF multiplexer also includes, for example, a first quadrature hybrid coupler (QHC), a second QHC and a third QHC. A coupling of the first QHC, a first pair of filters, and the second QHC separates the first frequency band and the second frequency band from the common port to the first port and to the second port, respectively. A coupling of the first QHC, a second pair of filters, and the third QHC separates the first frequency band and the third frequency band from the common port to the first port and to the third port respectively.