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Home > Products > Optical Phase Demodulators > 90-Degree Optical Hybrid
90-Degree Optical Hybrid  
Optoplex 90º Optical Hybrid - QPSK Demodulator
Optoplex 90º Optical Hybrid - QPSK Demodulator
PDF Datasheet
White Papers
  • Description
  • Features
  • Applications
  • Parameter Definition
Product Description - Optical Hybrid

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.

For optical coherent detection, the six-port 90° optical hybrid would mix the incoming signal with the four quadratural states associated with the reference signal in the complex-field space. The optical hybrid would then deliver the four light signals to two pairs of balanced detectors. See below block diagram for 90° optical hybrid and a coherent receiver.

Application of Optoplex optical hybrid

Optoplex's passive free-space micro-optics-based 90º optical hybrid is suitable for coherent signal demodulation for either homodyne or heterodyne detection. The patent-pending, broadband device accepts the two optical signals (S & L) and generates four output signals: S+L, S-L, S+jL, S-jL, as shown below. When these signals are detected by two balanced receivers, both the amplitude and the relative phase information between the input signals can be extracted via differential detection and digital signal processing. Moreover, in a coherent system, the preservation of the optical phase can be used to cost-effectively compensate optical transmission impairments in the electrical domain. For detailed introduction, please read Optoplex White Paper on Optical Hybrid.

Features and Benefits of Optical Hybrid:
  • Purely passive device (no need for external electric power)
  • Compact size
  • Based on free-space bulk-optics design
  • DPSK modulation is a prerequisite for adapting coherent detection
Applications of Optical Hybrid
  • For coherent signal demodulation and detection
  • For the next-generation optical transmission system
  • Key component for the optical coherent detection (a detection format which has been widely used in many other communication methods, such as radio and wireless)
Parameter Definition of Optical Hybrid

Parameter Definition


Wavelength Range (nm) is defined as spectral range over which the optical hybrid can operate.

1527.99 ~ 1563.05 nm

Phase Difference (deg): In each of the four output ports (M1, M2, M3 and M4), the interference between S and L takes place. If the phases of S and L at the four outputs are,
fSM1, fSM2, fSM3, fSM4, fIM1, fIM2, fIM3, fIM4
then, the phase difference between port 1 and port 3 is defined as:
(fSM1 - fIM1) - (fSM3 - fIM3)
The phase difference between port 2 and port 4 is defined as:
(fSM2 - fIM2) - (fSM4 - fIM4)

90±5 deg

Input Port: There are two input ports, which are S and L.


Output Port: There are 4 output ports, which are M1, M2, M3 and M4.


Excess Insertion Loss (dB) is defined as the actual insertion loss subtracted by 6 dB, which is the ideal intrinsic loss from any input to any output.

8.0 dB

Insertion Loss Difference (dB): It is the insertion loss difference between two specified optical paths.

0.5 dB

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

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

15 to 35 °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 optical hybrid product, please provide the following parameters:
  • Wavelength range
  • Fiber length
  • Optical connector type