A Wide-band Fiber Optic Frequency Dxstribution System Employing Thermally Controlled Phase Compensation*

An active wide-band fiber optic frequency distribution system employing a thermally controlled phase compensator to stabilize phase variations induced by environmenkal temperaiure changes is described. The dishibution system utilizes bidirational ddwavekng th transmission to provide optical feedback of induced phase variations of 100 MHz signals propagating along the distribution cable. The phase compensation considered here difirs from earlier narrow-band phase compensation designs in that it uses a thermally controlled fiber delay coil rather than a VCO or phase modulation to compensate for induced phase van'ations. Iko advantages of the wide-band system over earlier designs are [I) that it provides phase compensation for aU transmitted frequencies, and ( 2 ) the compensation is applied aper the optical inteterface rather than ekctronically ahead of it as in earlier schemes. Experimental resulfs on the first protqpe shows that the thermal stabilizer reduces phase variations and AUnn deviation by a factor of forty over an equivalent uncompensated fiber optit dishibution system.