  In this article, the performance of a fixed grid network is examined for
various modulation formats to estimate the system's capacity and spectral
efficiency. The optical In-phase Quadrature Modulator structure is used to
build a fixed grid network modulation, and the homodyne detection approach is
used for the receiver. Data multiplexing is accomplished using the Polarization
Division Multiplexed technology. 100 Gbps, 150 Gbps, and 200 Gbps data rates
are transmitted under these circumstances utilizing various modulation formats.
Various pre-processing and signal recovery steps are explained by using modern
digital signal processing systems. The achieved spectrum efficiencies for
PM-QPSK, PM-8 QAM, and PM-16 QAM, respectively, were 2, 3, and 4 bits/s/Hz.
Different modulation like PM-QPSK, PM-8-QAM, and PM-16-QAM each has system
capacities of 8-9, 12-13.5, and 16-18 Tbps and it reaches transmission
distances of 3000, 1300, and 700 kilometers with acceptable Bit Error Rate less
than equal to 2*10-3 respectively. Peak optical power for received signal
detection and full width at half maximum is noted for the different modulations
under a fixed grind network.
