In optical fiber communications, Mode –Division Multiplexing in combination with Wavelength Division Multiplexing and advanced modulation formats like QPSK n-QAM are utilized to deliver more amounts of data through a single fiber. For amplifying the signals in the long haul optical fibres link Few –Mode Erbium –Doped Fiber Amplifier is employed to equally and efficiently amplify both modes and respective wavelengths over the telecommunication C-band frequency range. In this paper A Dual-Carrier PM-QPSK transmission system is proposed for enhancing data rate with reduced bit error due to the cross section generated by the optical fibre non-linear properties. The spectrally efficient high bitrate transmission has generated in coherent systems. Using two PM-OPSK carriers, one can reduce transmitter bandwidth requirement to half compared to standard single carrier PM-QPSK while still supporting the same total bitrate. The total bitrate for this layout is given as 40Gbps. The 100-Km of fibre is modelled via a loss element and the fiber dispersion is modelled by an FBG model. Low transmitted power values in coherent systems typically give lower nonlinearity. Each sub-carrier is modulated by 21.4Gbps including FEC overheads. That means each polarization of a carrier is modulated by 10.7Gbps implying the symbol rate of 5.35 GHz. In order to minimize the crosstalk between the two carrier, the separation between them is kept half the symbol rate. As a result, when one carrier is at maximum, the other is at its minimum. The proposed scheme is utilized for both linear and non-linear fiber.