The Study On All Optical Clock Recovery In The All Optical 3R Regeneration

As the increase of demand for communication capacity, optical-transport-network develops toward high speed and long haul, and all-optical network finally. However, the transmission distance and speed are limited, because the signal is degraded caused by the dispersion and nonlinear effects during transmission. All-optical 3R is the very technology developed to solve this problem. The all-optical clock recovery is the key of all-optical 3R and all-optical network. All-optical clock recovery using F-P filter is chiefly talked about in this thesis.Work is carried out to study the wavelength conversion basing on cross gain modulation (XGM) of SOA and how it being affected by kinds of external and internal parameters of SOA , then it is simulated using the software named Optisystem3.0. The corresponding experiment is finished successfully after all the parameters being considered, and it prepares for the wavelength conversion used in clock recovery.It is analyzed theoretically of how SOA affects the modulation-depth of the signal according to the transport function of SOA about frequency,and a conclusion is given: the low-frequency can be suppressed by SOA. Then it is proved through experiment. F-P filter is analyzed theoretically in detail as the key component in all-optical clock recovery. Then, how the differential finesses of F-P filter and the excursion of the central wavelength of laser affecting the clock recovery are simulated using Optisystem3.0.For good result in all-optical decision, the scheme of all-optical clock recovery is plotted as follows: first, the information carried by the carrier is transferred to the continuous wave from a laser with steady central wavelength, then clock is recovered using F-P filter. It is simulated using Optisystem3.0, and the extinction-ratio of the clock is improved using a narrow-band-pass filter with enough narrow bandwidth and a little excursion of its center to the central wavelength of the laser, on the other hand, the low frequency noise in the clock is suppressed using SOA.40Gbps clock is recovered successfully using this scheme through comprehensive experiment. Not only the validity of previous work is proved, but also good experiment results are accomplished.