European Space Agency

PICSAL - Photonic Integrated Comb for Space AppLications


The project objectives are to design, fabricate, package, and integrate into a driver module for the first time, the Pilot Photonics comb source technology. A broad range of tests are considered within the scope of the project, including space environment testing, chip-level and module-level characterisation, and application level testing for communication applications, and swept-mode sensing applications.


Key Challenges are:

  1. To design and fabricate an ultra-low cost, size, weight, and power photonic integrated optical comb source
  2. To develop a custom optical package that meets all of the electrical, RF, and optical requirements, while also being suitable for the harsh environments of space
  3. To demonstrate the potential of this technology across a range of different space-relevant applications.


At its simplest, a single optical comb source can be used to replace an array of single mode lasers yielding cost, size, weight and power benefits. Pilot’s comb source is based on photonic integration so a tiny semiconductor chip produces the optical comb. This results in the world’s smallest and lowest cost optical comb source. In addition, there are application specific benefits of products based on the PICSAL comb technology. For example, in inter-satellite communication, the benefit is multiple data carrying wavelengths from a single chip and therefore higher data throughput. For atomic clocks the benefit is that Pilot’s technology can create a dual coherent mode optical signal which is ideal for coherent population trapping. Finally, Pilot’s comb source offers the ability to tune the wavelength spacing with very high accuracy and speed enabling a unique swept mode operation that is beneficial for gas, and fiber sensing,

Through PICSAL we have developed an evaluation unit that customers can use to experience these benefits for themselves (Figure 1).


The product that is delivered through PICSAL is a photonic integrated comb source evaluation module. The features are as follows:


  • Multiple coherent optical wavelengths from a single laser
  • C-band operation
  • Continuously tunable comb spacing over several GHz
  • Fiber coupled output
  • Standalone system with turnkey operation
  • Software controllable via USB connection
  • Video-cassette sized module in rugged metalised housing


Application specific feature examples:

  • For use in an atomic clock, an optical comb can be generated with a wavelength spacing that locks to the required microwave resonance
  • For frequency generation, the spacing between each comb line can be accurately set, and then any pair of comb lines can be selected and beaten together to generate a carrier of the desired frequency
  • For communication, each wavelength can be separated and modulated with independent data to increase total throughput
  • For FBG sensing, the wavelengths can be swept with high accuracy and speed to form a miniature FBG interrogator source
  • For gas detection and analysis, the comb can be used to lock to the spectral “fingerprint” of a particular species in a multi-gas environment

System Architecture

The high-level system is a laser driver module which is software controllable.

Its inputs are:

  • electrical power,
  • RF signal, and
  • computer control.

Its output is:

  • a comb of wavelengths around 1550nm on a polarization maintaining optical fiber. 

Internally, it consists of a packaged optical comb source PIC mounted on a PCB which drives the laser using four independent current controllers, and a single temperature controller. 

The main items to be developed are:

  • the comb PIC (photonic integrated circuit),
  • the laser package,
  • the RF source, and
  • the overall laser driver module (Figure 2)


Three simple phases are envisaged in the project:

  • Design,
  • Fabrication, and
  • Prototyping and Test 


  • M1: Design Review
  • M2: Acceptance Tests
  • M3: Final Review

Current status

Project successfully completed.

Status date

Tuesday, September 18, 2018 - 09:49