Lu Li

Graduation Semester and Year




Document Type


Degree Name

Doctor of Philosophy in Electrical Engineering


Electrical Engineering

First Advisor

Michael Vasilyev


We experimentally demonstrate, for the first time to our knowledge, a stand-alone all-optical regenerator capable of simultaneous 2R regeneration of multiple WDM channels. Recently, our group has proposed an all-optical 2R regeneration scheme for multiple WDM channels. This novel multi-channel regenerator is a modified configuration of Mamyshev 2R regenerator, in which a conventional highly-nonlinear-fiber (HNLF) is replaced by a novel group-delay-managed (GDM) nonlinear medium. The proposed multi-channel regeneration scheme uses multiple concatenated GDM unit cells, where each unit cell contains a piece of HNLF and a periodic-group-delay device (PGDD). Afterwards, the proof-of-principle experiment has also been demonstrated by using a recirculating loop to emulate of cascading multiple “fiber + PGDD” unit cells. However, the recirculating-loop-based regenerator is impractical and not useful in a real WDM systems. To make proposed regenerator practical, we build a GDM nonlinear medium with 4 or 6 “fiber + PGDD” unit cells, assisted by bi-directional Raman pumping. In this dissertation, we build a stand-alone all-optical multi-channel regenerator and present our experimental results on 3-channel all-optical 2R regeneration with 100 GHz spacing and 200 GHz spacing, as well as 100-GHz-spaced 12- and 16-channel 2R regeneration. We first investigate 2R regeneration performance for 3 channels in a GDM nonlinear medium containing four “fiber + PGDD” unit cells in 200 GHz spacing case and 100 GHz spacing case. The experimentally observed 2 dB eye-opening improvement confirms that few-channel performance is not degraded by narrower 100 GHz channel spacing. Then, the 100-GHz-spaced multi-channel regeneration experiments were performed with as many as 12 channels (12 × 10 Gb/s), and, further, 16 channels (16 × 10 Gb/s) by employing a GDM medium with 6 unit cells. All 16 channels demonstrate eye-opening improvement better than 5 dB at BER level of 10–9. In addition, we make investigations of a nonlinear-optical-loop-mirror (NOLM) based all-optical regenerator that can be used in phase-encoded systems. We experimentally demonstrate, for the first time to our knowledge, a NOLM-based phase-preserving amplitude regeneration of high-duty-cycle (50%) RZ-DPSK signals degraded by amplitude jitter and amplified spontaneous emission (ASE) noise, confirmed by a 1.5 dB eye-opening improvement. To show the path to extending the multi-channel regeneration capability to more advanced modulation formats, we propose a novel all-optical scheme of 16-QAM signal regeneration. The scheme consists of phase-sensitive amplifiers (PSAs), which are used to de-multiplex two quadratures, and new 2R regenerators, which are used for two-level amplitude signals. In the simulation, the capability of the regenerator has been demonstrated by constellation analysis. The modeling results show regenerated out signals have more than 4 dB signal-to-noise ratio (SNR) improvement on all 16 states compared to the degraded input signals.


Nonlinear optics, All-optical regeneration, Fiber optics


Electrical and Computer Engineering | Engineering


Degree granted by The University of Texas at Arlington