Transmissive Fiber Bragg Grating-Based Delay Line Interferometer for RZ-OOK to NRZ-OOK Format Conversion

Xin Liu,Miguel A Preciado,Lin Zhang,Xuewen Shu,Zuowei Xu,Hui Cao,Adenowo Gbadebo,Jiabi Xiong,Yu Yu

doi:10.1109/access.2019.2938021

Abstract

We propose a return-to-zero on-off keying (RZ-OOK) to non-return-to-zero (NRZ) OOK conversion scheme based on a transmissive phase-modulated fiber Bragg grating (PM-FBG). The PM-FBG has a spectrum similar to the combination of a delay line interferometer and a narrow band optical filter, which is designed and synthesized using numerical optimization algorithm. The coupling strength of the PM-FBG is almost uniform and the grating period varies along the fiber length according to the optimization method. The designed PM-FBG has been fabricated using advanced ultraviolet laser inscription technique. Experimental results show that such a PM-FBG can perform RZ-OOK to NRZ-OOK format conversion successfully.

Highlights

All-optical format conversion enhances the flexibility between different formats in future optical [1]
The transmissive fiber Bragg grating (FBG) has an almost uniform coupling strength while its period varies along the fiber length, which is the so-called phase-modulated FBG (PM-FBG) [18], [19]
We can see that a clear 25 ps delay is realized, which confirms the functionality of the designed phase-modulated fiber Bragg grating (PM-FBG)

Summary

INTRODUCTION

All-optical format conversion enhances the flexibility between different formats in future optical [1]. Various all-optical conversion schemes from RZ to NRZ have been proposed and demonstrated. These schemes can be classified into two categories, namely time domain based solutions and frequency domain based solutions. All the FBG-based methods proposed before make use of FBGs in reflection [12]–[16], which requires an additional coupler or circulator to assist the conversions. The transmissive FBG has an almost uniform coupling strength while its period varies along the fiber length, which is the so-called phase-modulated FBG (PM-FBG) [18], [19] This phasemodulation profile can be directly encoded in a phase mask, which can be potentially developed to a highly reproducible fabrication process

PRINCIPLE AND METHOD

EXPERIMENTAL DEMONSTRATION

CONCLUSION