LASER FOR PROVIDING PULSED LIGHT AND REFLECTOMETRIC APPARATUS INCORPORATING SUCH A LASER

A laser for generating laser light pulses comprises a cavity containing a n active optical gain medium (102) and a spectral filtering device (104), a delay device (110) for delaying light by a predetermined delay time (.DELTA. t), means (106) for extracting a portion of laser light from the cavity, lau nching said portion into said delay means (110) and returning the delayed po rtion to the optical gain medium (102), control means (116) operable to acti vate the gain medium for a first time period (Cl) to produce a first laser l ight pulse (LPl) having a duration that is less than the delay time (.DELTA. t), and activate the gain medium for a second time period (C2) while a said delayed portion of the first light pulse that has been delayed by the delay means (UO) is traversing the gain medium (102), thereby to produce a second laser pulse (LP2) having a shorter duration and faster risetime than the fir st laser light pulse (LPl), and output means (108) for .sigma.utputting the second laser light pulse (LP2).