Tunable optical attenuator (TO A) is an important device in optical communication system.An optically controllable variable optical attenuator (VOA) is studied.The device consists of side-polished fiber (SPF) with a photoresponsive liquid crystal (LC ) overlay.At an environmental temperature of 45℃,the tuning range of the opti cally controllable VOA is about 15dB.It is proved clearly that the tuning is reversib le and repeatable with periodic pumping beam illumination and the response time is less than 5s.The photoresponsive liquid crystal transforms from a light-scattering state into a light transparent state with the help of photoirradiation,and the refractive in dex of the liquid crystal layer changes.It results in optical loss variation of the signal light.With the structure optimization of the side-polished fiber and the new mixture liqui d crystal,the tuning range will be larger and the responding time will be shorter.The optical ly controllable VOA has simple structure and the cost is low.It connects with othe r fiber devices conveniently and has potential use in an all-fiber telecommunication sy stem.