Burst mode timing recovery speeds up optical network signal processing
Burst-mode timing recovery based on fourth-power phase detector for passive optical networks
Networking and Internet Architecture
Summary
Optical networks that carry internet data need to handle very fast signals, but the equipment for the fastest speeds is hard to build. The authors found a way to use slower hardware combined with smart digital processing to keep up with faster signals. They designed a new method that quickly figures out the timing of these signals without needing extra setup steps, so the system works faster and uses less power. This method is especially good for networks that send data in short bursts, like the 50G passive optical networks.
What this means in practice
- •For optical network engineers: Implement faster timing recovery in burst-mode optical receivers to reduce delay and power usage for 50G passive optical networks.
- •For telecommunications hardware designers: Design digital signal processing chips that use slower ADCs but still handle 50Gb/s signals efficiently using the proposed timing recovery method.
Authors
Ji Zhou, Haide Wang, Xiaofeng Zhang, Zhiyang Liu, Miao Yu, Changyuan Yu, Liangchuan Li, Xiangjun Xin
Abstract
Driven by the ever-increasing capacity demands, 50G passive optical network (50G-PON) is ready for practical application. It is highly challenging to realize 50GHz burst-mode analog components; therefore, based on 25GHz burst-mode analog devices, burst-mode digital signal processing (DSP) is introduced to achieve the reception and processing of 50Gb/s on-off keying burst signals. To optimize the power consumption and area of the DSP chip, a one-sample-per-symbol (1-SPS) analog-to-digital converter has been applied in 50G-PON. One of the main challenges is implementing burst-mode timing recovery (BM-TR) for the 1-SPS burst signal in 50G-PON. In this paper, we first propose a BM-TR based on the fourth-power phase detector (4PPD) for 50G-PON. We mathematically verify that 4PPD can directly compute the timing phase offset (TPO) from the 1-SPS signal without using training sequences, allowing for immediate BM-TR initialization within 20 cycles to prevent long convergence times. After the initialization, the feedback loop structure tracks the TPO changes based on the sign of 4PPD, the loop filter, and the numerically controlled oscillator. In conclusion, training-sequence-free 4PPD-based BM-TR achieves low burst overhead via fast convergence and is particularly effective for handling burst signals in 50G-PON.