Proximion's DCM Principle 

Dispersion (pulse broadening) is compensated for by precisely chirped FBGs allowing faster wavelengths to travel longer distances than slower, thereby reshaping the pulse. Without FBGs the pulses will eventually start to overlap and bit errors will occur. 

Proximion is the only company that offers continuous FBGs, hence providing future proof solutions that are independent of channel plan and modulation format.

 
PRINCIPLE OF CHIRPED FBG TO COMPENSATE FOR CHROMATIC DISPERSION
 

illustration of how a fiber bragg grating (fbg) works
 

FBG Fundamentals

An FBG can be compared with a mirror that reflects a certain wavelength and transmits all others. By inscribing many of these mirrors at well defined distances, the reflected wavelengths can be controlled with very high accuracy.

 

FBG Production Process

FBGs are generated by exposing the core of a specially prepared optical fiber to a fringe pattern of ultraviolet light. (The core is typically no more than 5 μm in diameter i.e. a tenth of the diameter of a normal human hair). The ultraviolet light will locally create changes in the refractive index of the core. A change in refractive index will function as a tiny mirror, reflecting wavelengths that fulfill the Bragg criteria.

Our versatile and proprietary grating writing technology utilizes a two‐beam interferometer to create the fringe pattern. A highly accurate motion controller can sequentially add up these fringe patterns with sub nanometer precision over more than 10 meters.

By actively controlling the period of the fringe pattern basically any type of FBG can be generated. Grating characteristics such as wavelength range, reflection and dispersion compensation attributes are easily controlled via our software.

 
 
proximions unique fiber bragg grating production process using interferometric technology
 

Innovation in Every Nanometer

 
When producing our continuous dispersion products, we induce fringes of the Fiber Bragg Gratings every 500 nm with an accuracy of 2 nm, while moving the fiber at a speed of 4 mm per second. This can be resembled by placing poles between New York and Washington D.C. (360 km) at every 0.5 meters with an accuracy of 2 millimeters, while flying at a speed of 4 Mach at 10 kilometers’ height. In fact it is actually even tougher; the accuracy of two arbitrary poles placed 20 kilometers apart must not be more than 2 millimeters.

Krister Fröjdh, Vice President R&D