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Home > Products > Optical Phase Demodulators > DQPSK Demodulator
DQPSK Demodulator  
Optoplex DQPSK Demodulator - DPSK Demodulator
Optoplex DQPSK Demodulator - DPSK Demodulator
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  • Description
  • Features
  • Applications
  • Specification
  • Parameter Definition
Product Description - DQPSK Demodulator
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.

With DQPSK, the bandwidth of the drive electronics needs only be half of the bit rate. So 43 Gb/s signals can be generated with 21.5 Gb/s equipment. This allows system providers to achieve the expanded flexibility of reducing system cost by using low-speed drive electronics.

Optoplex's Optical DQPSK demodulator converts quadratural phase modulation into amplitude modulation over the entire C+L band in support of data transmission rate of 10 or 40 Gb/s. DQPSK demodulator is designed for the next generation optical communications systems utilized in commercial, defense 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.

  • DQPSK demodulator uses half the transmission rate to achieve the same data rate (20-Gb/s system for 40-Gb/s data rate, with four phase states instead of two in DPSK format)
  • Lower transmission rate saves cost on many other components and electronics and is more tolerate of dispersion
  • 20-Gb/s system is the highest transmission rate possible for the 50-GHz channel spacing
  • Optoplex’s DQPSK demodulator currently provides a convenient solution for this application by using two matched DPSK demodulators with phase off-set at ± π/4. The co-packaged single-core DQPSK demodulator is also under development

For DPSK demodulator or Delay Line Interferometer, please visit DPSK Demodulator page.

Features and Benefits of DQPSK Demodulator
  • Athermal design
  • C+L band coverage by a single device
  • Low temperature-dependent frequency shift (TDFS)
  • Low polarization-dependent frequency shift (PDFS)
  • Wide bandwidth
  • Low insertion loss & PDL
  • High power handling
  • Passive, semi-tunable and fully tunable operation
  • Suitable for both RZ and NRZ modulation format
  • Telcordia GR-1221 qualified
DQPSK Demodulator Applications
  • 5 or 20 Gb/s DQPSK Signal Reception
  • Data Rate Optimization
  • Extend Transmission Distances
Standard Specifications of DQPSK Demodulator




Wavelength Range (C-Band)  nm  1527 to 1567 
Wavelength Range (L-Band)  nm  1567 to 1607 
Free Spectral Range1 (FSR, ~1/2 of the nominal data rate, a few typical values are given)  GHz  10.7, 21.5, 28 or 32.5 
FSR Error2  %  < 1 
Insertion Loss2 (including all connectors)   dB  5.7 Typical; 6.0 Max 
Extinction Ratio2  dB  > 18 
PMD2  ps  < 0.1 
Return Loss  dB  > 40 
PDL2  dB  < 0.2 
PDFS2  deg  < 3 
Optical Path Delay2 (Skew, among Input -> I1, I2, Q1, Q2)  ps  < 1.0 
Tuning Range  FSR  > 1.5 
Tuning Time Constant3  sec  < 1.0 
Power Consumption  W  1.0 Typical; 2.0 Max 
Tuning Voltage  V  0 to 5 
Maximum Input Optical Power   mW  300 
Operating Temperature  °C  -5 to 65 
Storage Temperature  °C  -40 to 85 
Dimension (L x W x H)4  mm  50x41x11  
Connector Type  -  TBD 
Fiber Pigtail Type  -  SMF-28 with 900 µm loose tube 
Fiber pigtail length  m  1.0 ± 0 


  1. Values listed are typical examples, customer can specify.
  2. Over the stated spectral and operating temperature ranges and all polarization states.
  3. Defined as the time required to reach half-way from the starting and ending points.
  4. Not including five collimator sleeves extending from one longer side by 21 mm.
Parameter Definition of DQPSK Demodulator

Parameter Definition


Wavelength Range is defined as spectral range over which the DQPSK demodulator can operate.

1528.77 ~ 1563.86 nm

DPSK is acronym for Differential Phase-Shift Keying


DLI is acronym for Delay Line Interferometer.


DQPSK is acronym for Differential Quaternary Phase-Shift Keying


DPSK Demodulator is a component that converts phase modulation into amplitude modulation.


Insertion Loss (dB) is the relative peak power level transmitted to the output ports referenced to the 0-dB reference level when the DPSK demodulator is inserted. "On" and "Off" ports are reported separately.

1.7 dB

Insertion Loss Uniformity (dB) is defined as maximum insertion loss difference between the adjacent channels of the two output ports across the whole operating wavelength range.

0.5 dB

Isolation/Extinction Ratio (dB) is defined as the power difference between peak and valley of the spectrum. "On" and "Off" ports are reported separately.

18 dB

Polarization Dependent Loss (PDL) (dB) is the power difference between the two extreme polarization states. "On" and "Off" ports are reported separately.

0.2 dB

Polarization Dependent Frequency Shift (PDFS) (deg) is the maximum frequency difference measured at the valley of power spectrum among all polarization states.

3 deg

Optical Return Loss (dB) is the ratio between the input power and the reflected power over all polarization states at each port , RL = -10×log10(Pr/Pin).

40 dB

Tuning Range (TR) (GHz) is the maximum shift variation of a center frequency of the spectrum driven by applying control voltage to DPSK demodulator.


Tuning Speed (TS) (second) is the time needed by the device to tune the frequency to its half of target position.

1 s

Operating Temperature (°C) is the ambient temperature range over which the device's performance spec can be met.

-5 to 65 °C

Storage Temperature (°C) is the ambient temperature range over which the device can be stored without affecting its intended application afterwards.

-40 to 85 °C

Product Request and Ordering Information
Please speak to Optoplex Sales persons. If you request custom-designed DQPSK demodulator product, please provide the following parameters:
  • Wavelength range
  • Free spectral range (FSR)
  • Passive, semi-tunable or fully tunable
  • Fiber length
  • Optical connector type