The Simplified Coherent Detection Technique For Ultra-Dense Wavelength Division Multiplexing Passive Optical Network (UDWDM-PON)

With the emerging broadband services,especially the explosive development of 8K high-definition(HD)video,virtual reality,and network video broadcasting,the user demand of bandwidth in access network is ever increasing.Fiber optical access network has the potentials to solve the problem,especially ultra-dense wavelength division multiplexing-passive optical network(UDWDM-PON)is recognized as one of the best solutions for next-generation PON,due to the advantages of multi-user access,high transmission bandwidth,data transparency,and network security.Furthermore,using the multi-core fiber to achieve the enhancement of access capacity is one of the potential solutions to achieve ultra-high capacity of UDWDM-PON.To avoid the use of expensive arrayed waveguide grating(AWG),it is ideally desired for UDWDM-PON to adopt polarization independent simplified coherent receiver which can heavily reduce the access cost.Since the access network is extremely sensitive to the cost,we propose to use 3x3 coupler to realize the optical mixing,instead of the traditional 90° optical mixer,with a simple configuration and low cost.Meanwhile,the space division multiplexing(SDM)technique based on multi-core fiber and polarization independent coherent receiver in UDWDM-PON have been investigated.The main outcomes of thesis are summarized as follows,(1)The 4-level pulse amplitude modulation(PAM-4)signal is used as the advanced modulation format of UDWDM-PON.We investigate the polarization independent simplified coherent detection scheme for PAM-4 signal.(2)We experimentally demonstrate C-band 10Gbit/s PAM-4 signal transmission over 40 km standard single mode fiber(SSMF)using polarization-independent simplified coherent receiver,including one 3x3 coupler,one polarization beam splitter(PBS),and three single-ended photodetectors(PDs).Without the use of digital signal processing(DSP),we can achieve the receiver sensitivity of-24 dBm at the 7% hard-decision forward error correcting threshold(Hard-FEC),(3)We propose a UDWDM-PON architecture based on multi-core fiber.The optical line terminator(OLT)uses optical frequency comb to generate multiple wavelengths,instead of multiple lasers to generate multi-wavelength.The optical distribution network(ODN)adopts multi-core fiber to realize system capacity enhancement with the help of space division multiplexing.The optical network unit(ONU)adopts polarization-independent simplified coherent receiver to demodulate the downstream signals.The ODN can be re-used with current time division multiplexing-PON(TDM-PON)infrastructure,because the AWG is replaced with the traditional optical coupler.