Fiber Optic attenuator is used to reduce the optical power level of a communication signal, in an optical fiber used in a fiber optic communication link. Fiber Optic Attenuators use different principles of functioning like gap-loss, absorptive or reflective techniques. Three basic types of Fiber opticl attenuators are step wise variable, continuously variable and fixed.

Fixed Value Fiber Optic Attenuators
Fixed value fiber optic attenuators have fixed values that are specified in decibels. Their applications include telecommunication networks, optical fiber test facility, LAN and CATV systems. Fixed value fiber optic attenuators are composed of four groups: Fixed Plug in Fiber optic attenuator, Fixed Standard Adapter Fiber optic attenuator , Fixed In-line  Fiber optic attenuator, and Fixed Hybrid Adapter Fiber optic attenuator.

Fixed Plug in Fiber Optic Attenuator has a male end and a female end.
Fixed Standard Adapter Fiber Optic Attenuator  (bulk head type) has a female end and a female  end.
Fixed In-line Fiber Optic Attenuator has a fiber cable terminated with two connectors which you can specify types.
Fixed Hybrid Adapter Fiber Optic Attenuator has a female end and a female end with different kind.

Variable Fiber Optic Attenuators
Variable Fiber Optic Attenuators come with many different designs. They are general used for testing and measurement, but they also have a wide usage in EDFA for equalizing the light power among different channels. Variable Fiber optic attenuators are composed of three groups: Variable plug in  type, Variable adapter type, Variable In-line type and Manual VOA type:

Variable Plug in  Fiber Optic Attenuator has a male end and a female end.
Variable Adapter fiber Fiber Optic Attenuator (bulk head type) has a  female end and a female end.

Variable In-line Fiber Optic Attenuator and Manual VOA Fiber Optic Attenuator are with more accurate attenuation compared with traditional connector type fiber optic attenuators, this fiber optic attenuator is with a precision screw set, by turning it, the attenuation range can be varied and this fiber attenuator can be with various terminations on the each side of the cable.