Optical frequency comb noise spectra analysis using an asymmetric fiber delay line interferometer

Abstract

A simple and practical apparatus enabling repetition rate (frep) noise, carrier-envelope frequency (fceo) noise and nth optical comb mode (νn) noise spectra measurements with high precision is established. The frep and νn noise spectra are measured by a fiber delay line interferometer, while fceo noise spectrum is measured by an f-2f interferometer. We utilize this apparatus to characterize the noise performance of an Er-fiber optical frequency comb (OFC) and analyze the origin of dominant noise sources. Moreover, this apparatus provides a powerful tool for diagnosing noise dynamics intrinsic in mode-locked lasers and OFCs. To this end, we uncover the anti-correlation between frep and fceo noise as well as the impact of servo loops on noise characteristics in the stabilized OFC.

Fiber-delay-line-referenced optical frequency combs: three stabilization schemes

“…The output heterodyne beat is detected, filtered, amplified, and finally mixed with 2f mod . Through division of the mixing result's voltage PSD by the fiber delay line's transfer function [28,29] , phase noise of the fiber delay line could be retrieved, as represented by the gray curves in Figs. To summarize, we compared three distinct stabilization schemes using a fiber delay line as a reference: (i) 1566 nm comb modes are stabilized to a fiber delay line and the repetition rate is stabilized to a signal generator; (ii) 1566 nm comb modes and repetition rate are stabilized to a fiber delay line; (iii) 1526 nm and 1566 nm comb modes are stabilized to a fiber delay line.…”

“…1. Detailed configuration of the AFI could be found in our previous publication [28,29] . The heterodyne beat from the interferometer carries the frequency noise p • δτnf rep f ceo 2f mod , where p accounts for the entire number of comb lines within the DWDM's bandwidth.…”

Noise Measurement and Reduction in Mode-Locked Lasers: Fundamentals for Low-Noise Optical Frequency Combs

“…In the same manner as the OH technique, after two heterodyne beats (at twice the center frequency of AOFS's driving frequency) are detected, the timing jitter PSD could be obtained through mixing these two heterodyne beats. Figure 4 shows the timing jitter PSD of a NALM Er-fiber mode-locked laser characterized by the DOH technique [45]. In this case, the measurement resolution is 10 −7 fs 2 /Hz level at 100 kHz offset frequency.…”

“…More importantly, several groups proved that the self-steepening effect induced timing jitter typically dominates timing jitter PSD in fiber mode-locked lasers due to their large intracavity nonlinear shift [44,45].…”

A Bidirectional FSO Communication Employing Phase Modulation Scheme and Remotely Injection-Locked DFB LD

“…Phase-modulated FSO communication requires a costly delay interferometer (DI) [14] or a sophisticated fiber Bragg grating (FBG) tilt filter [15], [16] to convert the phase-modulated optical signal into an intensity-modulated signal before being sent to a photodiode (PD). However, a costly DI or sophisticated FBG tilt filter will severely restrict the constructing of phase-modulated FSO communication.…”