Optical fiber amplifiers, such as erbium-doped fiber amplifiers (EDFA), are widely used in fiber optic communication systems. Their main function is to recover or amplify the strength of optical signal after it has been traveled or transmitted over a certain distance.
Traditionally, to recover the optical signal, electronic amplification was used where the transmitting optical signal was first converted into an electrical signal which was then amplified and then converted back into the optical signal. This practice made the overall amplification process of an optical signal costly and complicated. This process has been now simplified by EDFAs.
How does an erbium-doped fiber amplifier work?
EDFA modules, which are basically passive amplifiers, use an erbium-doped fiber so that the need for conversion of optical signals into electrical signals and then back into optical signals is eliminated completely.
At present, when it comes to optical amplification, an optical signal is amplified within the optical fiber by a laser that operates at a wavelength of 980nm or 1480nm. This laser excites erbium atoms, which then emit a large number of photons when triggered by a much weaker incoming optical signal at the same wavelength as the incoming optical signal.
This entire process results in an amplification of the input optical signal at the output of an EDFA.
Why does an EDFA need an optical filter?
Most telecom wavelengths function and operate in the C-band (1520nm-1570nm) or the L-band (1570nm-1620nm). That’s why the pump laser that acts upon the optical signal disrupts the precise wavelength, which is a significant issue in a fiber that accepts multiple communication channels.
In traditional EDFAs, a pair of filter components was used to rectify the EDFA’s output signal. A GFF (Gain Flattening Filter) or fiber bandpass filter is used to flatten or even out the outgoing amplified optical signal. This filter operates in accordance with a 980nm-blocking or 1480nm-blocking wavelength-division multiplexer (WDM). A WDM is also used to minimize the interference caused by the pump laser.
A thin-film fiber bandpass filter is designed to block or pass wavelengths of a certain band. While filters are designed using different technologies, one of the best filters is a fiber bandpass filter that is made based on environmentally stable thin-film filter technology.
You can easily implement this to block unwanted noise or unwanted signals in fiber amplifiers, as well as fiber laser systems.
Being an optical passive component, it is also characterized by high isolation, low insertion loss, high return loss, and excellent environmental stability. Some filters are also designed to handle high-power fiber amplifiers, fiber lasers, high-speed communication, and instrumentation systems.
If you are looking for high-quality fiber bandpass filters, contact DK Photonics. We are the leading manufacturer of optical passive components, including fiber bandpass filters for different operating wavelengths.