The Investigation On Key Techniques For Coherent Received40Gb/s/λ WDM-PON System

With the rapid development of the Internet, the broadband industry has been thriving, such as IPTV, HDTV and Three-Dimensional projection, etc., which has, therefore, triggered higher and higher demand for the transmission bandwidth of the Access Internet. Due to its high capacity, simple construction and transparent business support, the PON has evolved to be an important technology and has been widely applied. Amongst, WDM-PON is considered to be the optimal choice as the next generation of PON, because of its great advantages, such as, high bandwidth capacity, bearer service targeting various wave length, smooth and seamless evolution support. Furthermore, it is a valued direction to improve the WDM-PON system towards the single wave length at40Gb/s. However, the existing optical transmission technology cannot satisfy the system requirement, because its structure is too complicated and its cost is quite high. As a result, to define the optical transmission technology at40Gb/s that agrees with the WDM-PON system is of vital importance for promoting the advancement and application of40Gb/s/λ WDM-PON.An important technical approach for the system implementation is to launch up-load optical carrier wave under the Optical Line Terminal (OLT), which can effectively realize the colorlessness of the Optical Network Unit (ONU) and lower the cost. Meanwhile, Coherent optical receiver and electrical domains equalization, can effectively increase the coverage distance and reduce system structural complexity. Therefore, this paper is designed to explore the key relevant technology for the coherent light reception and electrical domains equalization.To be more specific, the research is carried out mainly from the following aspects:Firstly, an up-load transmission plan is proposed based on the improved duo-binary modulation for the N×40Gb/s/λWDM-PON system that can launch up-load optical carrier wave under the OLT. Since the MZ modulator is high-cost and sensitive to the polarization, an EA modulator is adopted to replace it, to the benefit of the improved duo-binary modulating system. Moreover, a simulation experiment been conducted to validate the feasibility of the plan.Secondly, a coherent reception plan is designed for the uploading of the single light source. In this scenario, the light source at the OLT will simultaneously generate local oscillator light and up-load light carrier wave, which can effectively enhance the sensitivity of the receiver, simplify the system as well as lower the cost.Lastly, a band-stop filter plan and a LMS algorithm-based dispersion compensation plan are suggested to restrain the Rayleigh scattered noise and dispersion existing in the colorless ONU schema that launches up-load optical carrier wave under the OLT. Besides, simulation tests have been carried out. The findings suggest that under such circumstance, the receiver sensitivity can be promoted to6dB to the maximum when the Rayleigh noise deteriorates. The designed scheme is effective for the dispersion compensation of the signal at40Gb/s within the distance of40kilometers.