Stabilisation of a fibre frequency synthesiser using acousto-optical and electro-optical modulators

A fibre-optic frequency synthesiser is developed that is stabilised to the optical frequency standard based on molecular iodine (Nd : YAG/I₂). The possibility of transferring stability of the optical frequency standard to other optical frequencies in the IR range 1–2 μm and to the RF range by using synthesiser phaselocked loops (PLLs) with acousto-optical and electro-optical modulators is experimentally demonstrated. The additive instability introduced into the optical frequency comb of the synthesiser (which arises due to PLL residual random errors) is several orders less than the intrinsic instability of the reference optical frequency standard employed (i.e., is noticeably less than 1 × 10^-13 for 1 s and 5 × 10^-15 for 1000 s).