Do you struggle with too much light saturating your fiber optic receiver? Enter the fiber optic attenuator, a passive device designed to reduce the power level of an optical signal. By using optical attenuators, you can achieve the best fiber optic system performance.
While multimode systems generally don’t require attenuators, single-mode systems, especially long-haul DWDM network links, require them to balance the optical power during transmission.
Fiber optic attenuators come in many different forms. In the market, you can find different types of optical attenuators classified by connector type, cable type and more.
Generally, they are grouped into fixed optical attenuators (FOA) and optical variable attenuators (VOA). You can also divide them into single-mode and multi-mode attenuators based on cable types.
As the name suggests, fixed attenuators are designed to have an unchanging level of attenuation in optical fiber, typically between 1dB and 30dB. The preferred optical attenuators often use either doped fibers, misaligned splices, or total power, while non-preferred attenuators often use gap loss or reflective principles.
There are two types of fixed value attenuators: in-line type and connector type. In-line type looks like a plain fiber patch cable, while connector type attenuator looks like a bulkhead fiber connector. These attenuators can be used in telecommunication networks, optical fiber test facilities, Local Area Network (LAN) and CATV systems.
Optical variable attenuators, or variable optical attenuators (VOA), use a variable neutral density filter. They are generally use for testing and measurement, but they also widely adopt in Erbium-Doped Fiber Amplifier (EDFA) for equalizing the light power among different channels.
There are two types of optical variable attenuators: stepwise variable attenuators and continuously variable attenuators.
Stepwise variable attenuators can change the signal attenuation in known steps such as 0.1dB, 0.5dB, or 1dB.
Continuously variable optical attenuators can provide a precise level of attenuation through flexible adjustment.
This allows operators to adjust the attenuator quickly and precisely without any interruption to the circuit.
In general, there are two situations where you may need fiber optic attenuators in your system.
One situation is when you need to reduce the receiver power.
Sometimes the signal arriving at the receiver is too strong and can overpower the receiving elements. This can be caused by a mismatch between the transmitters and receivers or the use of media converters designed for a much longer distance. In this case, you can install optical attenuators in the fiber optic link to reduce the signal power and properly match the signal level.
Another situation where you may need attenuators is when testing power level margins.
During testing, attenuators can be temporarily added to the system to add a calibrated amount of signal loss and test power level margins in the fiber optic system. With the transmitter turned on and using a fiber optic power meter set to the system operating wavelength, you can use the attenuator to test the system power.