Ultralow phase noise microwave generation with an Er:fiber-based optical frequency divider

TL;DR

This paper demonstrates an Er:fiber optical frequency divider capable of generating microwave signals with ultra-low phase noise comparable to cryogenic oscillators, advancing optical-to-microwave conversion technology.

Contribution

It introduces a novel Er:fiber-based optical frequency divider that achieves extremely low phase noise in microwave generation, surpassing previous methods in stability and noise performance.

Findings

Phase noise below -100 dBc/Hz at 1 Hz offset from 10 GHz

Shot noise limited phase noise at -145 dBc/Hz beyond 10 kHz offset

Comparable or better phase noise than cryogenic microwave oscillators

Abstract

We present an optical frequency divider based on a 200 MHz repetition rate Er:fiber mode-locked laser that, when locked to a stable optical frequency reference, generates microwave signals with absolute phase noise that is equal to or better than cryogenic microwave oscillators. At 1 Hz offset from a 10 GHz carrier, the phase noise is below -100 dBc/Hz, limited by the optical reference. For offset frequencies > 10 kHz, the phase noise is shot noise limited at -145 dBc/Hz. An analysis of the contribution of the residual noise from the Er:fiber optical frequency divider is also presented.