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.
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 utilized in commercial, defense and space exploration markets. The DPSK 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 polarization-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 polarization-dependent phase shift (PDPS) 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 tunable, semi-tunable or purely passive.
Optoplex provides three types of DPSK demodulators:
- Tunable DPSK demodulator
- Passive DPSK demodulator
- Semi-tunable DPSK demodulator
Tunable DPSK demodulator: A tunable DPSK demodulator is the DPSK demodulator whose spectral response can be tuned along the frequency axis while keeping the FSR unchanged.
Passive DPSK demodulator: To avoid system control involving complicated feedback algorithm and power consumption, a passive DPSK demodulator can be built. As indicated by its name, a passive DPSK demodulator does not have the tuning capability and its phase, or spectral constructive/destructive peaks, is fixed when it is built. By “passive” it means that the DPSK demodulator does not contain spectral tuning element in the device.
Semi-tunable DPSK demodulator: Considering the contribution of TDFS to the channel misalignment and that TDFS does not scale down with FSR as does the FSR-error, the passive solution will not work well for a low-bit-rate system. However, by combining the features of tunable and passive DPSK demodulators, Optoplex developed semi-tunable DPSK demodulator, also known as Colorless DPSK Demodulator. A colorless DPSK demodulator is a special tunable DPSK demodulator whose optical performance is the same as passive DPSK demodulator, but, like a tunable DPSK demodulator, equipped with a tuner for providing a few GHz tuning capability. Its FSR can be either 25 GHz or 50 GHz so that it can be used in systems with channel spacing being a multiple of the FSR. As a result, Optoplex’s colorless DPSK demodulator combines the advantages of both tunable and passive DPSK demodulators and can serve the ever-demanding needs of system providers.
Dual-Rate DPSK Demodulator is also available.
For DQPSK demodulator, please visit DQPSK demodulator page.