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Tunable optical filters Quantum applications
Quantum Communications

High performance spectral filtering for quantum applications

On: Mar 07, 2023

In: Quantum Communications

By: Marc-André Laliberté


Quantum science is a century-old field of study but recent technological advancements led to the enablement of new techniques to tap into the endless potential of quantum mechanic properties expressed at the single particle level.

One can now exploit the quantum superposition and quantum entanglement principles to setup un-hackable communication links, to detect infinitesimal force shifts, or to solve complex problems that outweigh previous super-computers. This requires controlling single atoms/ions, electrons and photons with high finess so that nothing interferes with the desired process

High quality optics is key in addressing this challenge, starting with the generation of “pure” photons with:

  • an extremely well-defined spectral profile
  • minimal noise
  • high isolation from initially co-generated signals
  • minimal pulse distortion

This calls for tailored solutions.

Tunable optical filters for quantum photonics


  • Quantum Key Distribution
  • Atomic Clocks
  • Quantum Computing
  • Quantum Sensing
  • Fundamental Research


  • Single-photons
  • Entangled photons
  • Optical tweezers
  • Cold Traps
  • Diamond defects

Objectives & Examples

Objectives & Examples

TeraXion’s optical filters rely on Fiber Bragg Grating (FBG) technology, reknown for enabling narrow bandwidths and high isolation in a practical and rugged format.
To these intrinsic advantages, TeraXion adds 20 years of optimizing design parameters and refining manufacturing skills to achieve unique features the most challenging applications need require.
Finally, the TFN tunable platform confers the benefits of the ultimate precision on the band position and an easy integration into commercial products.

Narrow bandwith

Ultra-narrow bandwith

QKD Components Boost Performance

QKD modulation and demodulation typically requires asymmetric Mach-Zehnder interferometers, phase modulators, polarization splitters and combiners, and quantum random number generators. Also, optical components like dispersion compensators and spectral filters are sometimes needed to improve system performance. One should note that the actual QKD protocol and the associated optical sub-systems are more complicated than this simplistic description (Fig.1), used to illustrate the role and importance of optical components, such as dispersion compensators, narrow broadband filters and low noise lasers.

Reducing excess loss is of prime importance on the quantum channel and in the receiver box on the Bob side, as any lost photon must, according to the QKD protocol, be considered as if it was measured by Eve, reducing the transmission rate of usable secure keys.

Parameters Values Units
Center wavelength λ (CWL) [700 — 1000] nm
Reflection Bandwidth [2 – 7]⁽¹⁾ GHz
[7 – 100] GHz
Center wavelength λ (CWL) [1525 — 1610] nm
Reflection Bandwidth [35 – 500] MHz
[2 – 100] GHz
Tuning range ±30 GHz
Tuning resolution 2 pm
Reflectivity [50 – 99.9+] %
Isolation⁽²⁾ [20 – 70⁽¹⁾] dB
Fiber type PM or non-PM

(1) By design
(2) Per FBG


CWL Typical usage
700–1000 nm Atoms/Ions cooling & trapping
Quantum dots excitation & emission
Diamond defects emission
Entangled photons generation (SPDC)
1525–1570 nm Telecom C-band sources & detection
Entangled photons generation (SPDC)
1590–1610 nm Telecom C-band sources & detection
Entangled photons generation (SPDC)