Fiber optic attenuators are devices which reduce (attenuate) the strength of a fiber optic signal within a fiber optic network. Attenuators are usually used when the signal arriving at the receiver is too strong and hence may overpower the receiving elements. This may occur because of a mismatch between the transmitters/receivers (transceivers, media converters), or because the media converters are designed for a much longer distance than for which they are being used. Sometimes Fiber optic attenuators are also used for stress testing a network link by incrementally reducing the signal strength (increasing the dB attenuation) until the optical link fails, thus determining the signal’s existing safety margin.

Our attenuators are a very high quality design using doped fiber to attenuate the signal. Our singlemode attenuators offer a operating wavelength range of 1250nm to 1600nm, covering both the common 1310nm and 1550nm operating wavelengths. The attenuation accuracy is +/- 0.5dB, up to 5dB and +/- 10% over 5dB. The return loss is >50dB for standard connectors and >60dB for APC connectors. Maximum transmission power is typically one watt. We stock Fiber optic attenuators for the following fiber optic connector types: ST, SC, SC/APC, FC, FC/APC, LC, LC/APC, MU. Other connector type attenuators are available upon special order. We stock most values between 1dB and 25dB for each of these attenuator types.

Although fiber optic attenuators are normally used in singlemode circuits, because this is where the stronger lasers are used for distance transmission, we also have multimode attenuators available (upon special order) in 50/125 and 62.5/125 fiber sizes. Since these will be custom made, minimum order quantity (50+) and extended lead time (2-4 weeks) may be required.

The most common version of Fiber optic attenuators are, as shown below, male to female units, often called plug-style or buildout style. These plug-style Fiber optic attenuators simply mount on one end of a fiber optic cable, allowing that cable to be plugged into the receiving equipment or panel. We also have female to female (bulkhead) attenuators, often used to mount in patch panels or for connecting two fiber optic cables together. More expensive, but useful for testing, are variable attenuators which are adjustable between 1dB and 30dB. We also can custom build in-line attenuators where the attenuator is incorporated within a fiber optic patch cable, built to your specifications.

The dB ratings are a measure of signal strength and can sometimes be confusing. The chart below will give you an idea of the percent of attenuation of your signal for specific dB values.wiki

Attenuation % (signal reduction) for different dB values
1dB = 21% / 6dB = 75%
2dB = 37% / 7dB = 80%
3dB = 50% / 10dB = 90%
4dB = 60% / 13dB = 95%
5dB = 68% / 15dB = 96.8%