Optical Phase Demodulators

Optoplex’s Optical DPSK Demodulator, also known as Delay Line Interferometer (DLI), converts phase modulation to amplitude modulation over the entire C+L band in support of data transmission rates of 2.5, 10 or 40 Gb/s. The DPSK demodulator is designed for phase modulated optical communication systems utilised in commercial, defence and space exploration markets. The device plays a key role in improving signal quality and performance to meet the expanding demand for higher data rates and more complex transmission formats within current and next generation systems without major capital expenditure. Optoplex’s DPSK Demodulator is based on a patented free-space optical design, which is compact, athermal and polarisation independent. The measured frequency drift over temperature is only ~0.02 GHz/°C for our standard passive device. Further, this DPSK Demodulator exhibits a total polarisation-dependent phase shift of less than 2 degrees over the entire operating temperature range with a high extinction ratio. Optoplex’s DPSK Demodulators can be configured to be fully tuneable, colourless tuneable or purely passive. Dual Rate DPSK Demodulator is also available.

Optoplex’s Optical DPSK Demodulator, also known as Delay Line Interferometer (DLI), converts phase modulation to amplitude modulation over the entire C+L band in support of data transmission rates of 2.5, 10 or 40 Gb/s. The DPSK demodulator is designed for phase modulated optical communication systems utilised in commercial, defence and space exploration markets. The device plays a key role in improving signal quality and performance to meet the expanding demand for higher data rates and more complex transmission formats within current and next generation systems without major capital expenditure. Optoplex’s DPSK Demodulator is based on a patented free-space optical design, which is compact, athermal and polarisation-independent. The measured frequency drift over temperature is only ~0.02 GHz/°C for our standard passive device. Further, this DPSK Demodulator exhibits a total polarisation dependent phase shift of less than 2 degrees over the entire operating temperature range with a high extinction ratio. Optoplex’s DPSK Demodulators can be configured to be fully tuneable, colourless tuneable or purely passive. Dual-Rate DPSK Demodulator is also available.

Optoplex's 2X4 polarisation diversified optical hybrid (aka QPSK Mixer) is a 2x4 device, which mixes an incoming signal with a local oscillator. The 4 outputs of this device are connected to 4 single-ended detectors (see the function diagram below). The device features a monolithic optical core integrating a PBS with an interferometer which is also widely used in Optoplex's interleaver and DPSK-demodulator platforms. This device is athermal, colourless, data-rate independent, compact in size and designed for manufacturability. This platform can also be extended to a 2X8 polarisation diversified hybrid to incorporate with 4 pairs of balanced detectors.BBN International supplies Optoplex, fibre optics, fiber optics, 2x4 QPSK mixer, 2x4, polarisation diversified

To be used for optical coherent detection such as DP-QPSK receivers, Optoplex’s ten-port 2x8 Coherent Mixer (aka QPSK mixer) combines the incoming signal with a local oscillator to generate eight light states in the complex-field space. The eight light output signals can then be coupled into four pairs of balanced detectors. The block diagram below shows the application of a 2x8 coherent mixer in a DP-QPSK receiver. Since the mixing process is data rate independent, the devices can be used for any data rate in applications such as 40Gb/s or 100Gb/s transmission systems.BBN International supplies Optoplex, fibre optics, fiber optics, optical mixer, qpsk, C-band, 2x8

Six-port hybrid devices have been used for microwave and millimeter-wave detection systems since the mid-1990s and are a key component for coherent receivers. In principle, the six-port device consists of linear dividers and combiners interconnected in such a way that four different vectorial additions of a reference signal (LO) and the signal to be detected are obtained. The levels of the four output signals are detected by balanced receivers. By applying suitable baseband signal processing algorithms, the amplitude and phase of the unknown signal can be determined.

Differential Quaternary Phase-Shift Keying (DQPSK) is the four-level version of DPSK. DQPSK transmits two bits for every symbol (bit combinations being 00, 01, 11 and 10) and has an additional advantage over conventional binary DPSK. DQPSK has a narrower optical spectrum, which tolerates more dispersion (both chromatic and polarization-mode), allows for stronger optical filtering, and enables closer channel spacing. As a result, DQPSK is the only modulation format which allows processing of 40Gb/s data-rate in a 50-GHz channel spacing system.BBN International supplies Optoplex, fibre optics, fiber optics, dqpsk demodulator

Optical differential-phase shift keying (DPSK) provides a desired modulation format that offers high receiver sensitivity, high tolerance to major nonlinear effects in high-speed transmissions, and high tolerance to coherent crosstalk. In DPSK, data information is carried by the optical phase difference between adjacent bits. For direct detection of DPSK signal (by conventional intensity detectors), a DPSK demodulator is needed to convert the phase-coded signal into an intensity-coded signal.BBN International supplies Optoplex, fibre optics, fiber optics, DPSK, demodulator, delay line interferometer