GRIFFON researchers will give two invited talks at the Progress In Electromagnetics Research Symposium (PIERS).
The 36th PIERS will be held in Prague, Czech Republic, European Union 6-9 July, 2015
G. Jacobsen, S. Popov, “Impact of Phase Noise in High Capacity Optical Coherent Transmission Systems”
Laser phase noise from the transmitter and Local Oscillator lasers strongly limits the performance of high capacity, high constellation coherent optical transmission systems. Using Digital Signal Processing techniques it is possible to mitigate the influence with specific form of the DSP for different modulation formats. In this paper we will present a number of possible mitigation techniques, applicable for such modulation schemes as N-level PSK and N-level QAM. It will specifically be shown that the circular QAM configuration has inherent significant added phase noise tolerance compared to the classical square configuration. The research has also been performed considering the so-called Equalization Enhanced Phase Noise, which appears as an added phase noise based impairment for coherent transmission systems with optically induced dispersion and digital (electrical) dispersion compensation. A novel understanding of the origin of EEPN and of straightforward mitigation techniques will be presented
- G. Jacobsen, M.S. Lidón, T. Xu, S. Popov, A.T. Friberg, Y. Zhang, “Influence of pre- and postcompensation of chromatic dispersion on equalization enhanced phase noise in coherent multilevel systems”, Journal of Optical Communications, vol. 32, pp 257 - 261, September 2011.
- T. Xu, G. Jacobsen, S. Popov, J. Li, A. T. Friberg, Y. Zhang, “Analytical estimation of phase noise influence in coherent transmission system with digital dispersion equalization”, Optics Express, vol. 19, pp 7756 – 7768, April 2011
X.Pang, A. El-Taher, R.Schatz, G.Jacobsen, S.Popov, S.Sergeyev,"Experimental Evaluation of Noise Impairments in Unrepeated Distributed Raman Amplified DP-16QAM SSMF Links"
Unrepeated fiber transmissions over hundreds of kilometers span with advanced modulation formats and DSP-based coherent detection schemes are considered as a potential candidate to meet the distance and capacity requirements in certain application scenarios where render amplification sites between terminals are impractical due to geographic, commercial or security constrains . Distributed Raman fiber amplifier (DFRA) ensuring a relatively constant power distribution of the optical signals along links can effectively improve the system OSNR and fiber nonlinearity tolerance, therefore is widely adopted in unrepeated transmission solutions. To date, unrepeated transmissions of 30 Gbaud DP-QPSK over 444 km , single and dual carrier 28 Gbaud DP-16QAM over 240 km [3, 4] have been demonstrated by using Raman amplification with large effective area fibers (LEAF). In this paper we report on a systematic experimental characterization of both the amplitude and phase impairments of the received signal induced by a bidirectional Raman pump at 1455 nm with an evaluation of the coherent transmission performances of a 28 Gbaud DP-16QAM signal in a standard single mode fiber (SSMF). The Raman induced amplitude and phase noise on the received 1550 nm signal is directly measured and the discussions around the operational rules and limitations are presented considering the inter-relation between pump power, signal OSNR and induced noise. Furthermore, performances of different carrier phase recovery algorithms, including decision-directed phase-locked-loop (DDPLL) , blind phase search (BPS)  and a two-stage QPSK partitioning  with variable filtering implementations in the DSP routine are investigated taking into account the specific noise profile of the received signal.
- “Applications for Distributed Raman Amplification”, Finisar white paper, 2012
- D. Chang et al., “8 x 120 Gb/s Unrepeatered Transmission over 444 km (76.6 dB) using Distributed Raman Amplification and ROPA without Discrete Amplification,” ECOC 2011, Tu.3.B.2.
- S. Oda et al., “80x224 Gb/s Unrepeated Transmission over 240 km of Large-Aeff Pure Silica Core Fibre without Remote Optical Pre-amplifier,” ECOC 2011, Th.13.C.7.
- G. Meloni et al., “Unrepeated Link Distance Increase for 448 Gb/s Channel Transmission by using Large Core Area,” OECC 2013, TuR1-2.
- R. Borkowski et al., “Anatomy of a Digital Coherent Receiver,” IEICE Trans. Commun., E97.B, 1528–1536, (2014).
- T. Pfau et al., “Hardware-Efficient Coherent Digital Receiver Concept With Feedforward Carrier Recovery for M-QAM Constellations,” J. Lightw. Technol., 27, 989-999, (2009).
- K. P. Zhong et al., “Linewidth-Tolerant and Low-Complexity Two-Stage Carrier Phase Estimation Based on Modified QPSK Partitioning for Dual-Polarization 16-QAM Systems,” J. Lightw. Technol., 31, 50–57 (2013).