1 This pdf, known as a phase portrait, is sensitive to waveform distortion and noise and contains unique signatures of impairments. Improving the amplifier's NF can increase OSNR, and the improved OSNR can be used to increase the system reach, reducing the channel power in order to suppress the nonlinearities, etc.Īsynchronous delay-tap sampling is an alternative to the eye diagram that uses the joint probability density function (pdf) of a signal x( t), and its delayed version x( t + Δ t) to characterize the signal. The required OSNR should be increased by 6 dB when the data rate is increased by a factor of 4. As an example, a typical OSNR requirement for BER=10 −9 is about 17 dB at 10 Gb/s data rate. The OSNR (in dB) of a signal channel at the end of the system is approximated by: OSNR (dB)=58+ P out− L span−NF−10 log( N amp), when the system has N amp fiber spans, span loss L span (in dB) followed by an optical amplifier with output power P out (in dBm) per channel launched into the span and noise figure (NF) (in dB). OSNR is defined as the ratio of the power of signal channel to the power of ASE in a specified optical bandwidth (conventionally 0.1 nm). In long-haul and undersea transmission system with many EDFA chains, OSNR is an important system parameter to design and characterize the optical transport system. The shape of the eye is generally broadened and distorted (i.e., eye is closed) due to limited bandwidth and fiber impairments, and noise and timing jitter are added onto this broadened and distorted eye shape. Figure 24b shows the eye diagram close to a real situation. Therefore, the eye diagram deviates from the perfect rectangular shape. In reality, the transmitter and receiver have a limited bandwidth with noise and jitter, and the transmission media (i.e., optical fiber) has dispersion and nonlinearites. When a perfect transmitter and receiver (i.e., infinite receiver bandwidth with zero noise characteristics and jitter), and a perfect transmission media (i.e., no dispersion and nonlinearites) are used, the received eye diagram is shaped as a perfect rectangular.
#NOISE MAPPING DIAGRAM SERIES#
A square bit stream (i.e., series of symbol ‘1’s and ‘0’s) is sliced into sub-bit stream with predetermined eye intervals (i.e., several bit periods), and displayed through bit analyzing equipment (e.g., digital channel analyzer), overlapping the sliced sub-bit stream in order to obtain the eye diagram. An eye diagram provides a simple and useful tool to visualize intersymbol interference between data bits.