onu and clock synchronization method of twdm‑pon system

Abstract

The invention also discloses an ONU (Optical Network Unit) for a TWDM-PON (Time and Wavelength Division Multiplexed-Passive Optical Network) system, and a clock synchronization method based on the same, and relates to the optical fiber communication field. The ONU comprises a passive wavelength division multiplexing WDM device, a plurality of photoelectric conversion devices, a selecting-two-from-multiple transposition circuit, an MAC (Medium Access Control) circuit, a CDR (Clock Data Recovery) circuit and a PLL (Phase Locked Loop) circuit, wherein the WDM device divides a combined wave optical signal received by the ONU to the independent optical channel corresponding to each wavelength; the optical signal of each wavelength is independently output through the optical channel corresponding to each wavelength; after the multi-wavelength combined wave optical signal received by the ONU is divided, the output optical signal of each wavelength can realize conversion from an optical signal to an electric signal through an independent photovoltaic conversion device; and each output optical channel is corresponding to one photovoltaic conversion device. The ONU for TWDM-PON system can flexibly select one of four physical ports for logic OLT (Optical Line Terminal) ports of the TWDM-PON as a clock source, and does not influence data communication, wherein a data channel is separated from a clock recovery channel.

Description

technical field [0001] The invention relates to the field of optical fiber communication, in particular to an ONU of a TWDM-PON system and a clock synchronization method. Background technique [0002] TWDM-PON (Time and Wavelength Division Multiplexed Passive Optical Network, time division and wavelength division multiplexing passive optical network) technology provides four pairs or more wavelengths in each fiber, and each pair of wavelengths can provide 2.5Gbps or 10Gbps symmetrical or asymmetrical rate In 2012, FSAN (Full Service Access Network, full service access network) designated TWDM-PON technology as the solution choice for the implementation of NG-PON2 (Next Generation Passive Optical Network, next-generation passive optical network) architecture. [0003] At present, TWDM-PON adopts four XG-PON (10-Gigabit-capable Passive Optical Network, 10-Gigabit-capable Passive Optical Network) stacked on different wavelengths, which can be combined with the existing GPON (Gi...

AI Technical Summary

Problems solved by technology

[0010] Since one OLT port of TWDM-PON has 4 PON MACs, there are 4 synchronous Ethernet upstream devices connected to 4 PON MACs, that is, one OLT port of TWDM-PON has 4 clock sources, and the TWDM-PON system Through the tunable optical wavelength filter, the ONU selects the multiplexed optical signals including λ1, λ2, λ3, and λ4 sent by the central office equipment (OLT). According to the wavelength channel selection signal, the tunable optical wavelength filter starts from λ1 , λ2, λ3, and λ4, select one of the optical signals with a wavelength of λx, and output it to the photoelectric conversion device in the ONU, that is, the clock of this wavelength actually recovered by the ONU, and there are 4 OLT ports If the clock needs to be synchronized to a clock other than λx according to the actual engineering use, or it is found that the other three wavelengths have channels with a higher clock level than λx according to the SSM clock level, it is impossible to implement the scheme of using a tunable optical wavelength filter

Therefore, the ONU of the traditional TWDM-PON system has the defect that it cannot flexibly select the clock source of the physical port of the OLT

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