What is 128-QAM ( state Quadrature Amplitude Modulation)?

QAM is Quadrature Amplitude Modulation is the modulation technique which provides significant benefits for data transmission techniques. It is widely used in many digital data radio communication and data communications applications. QAM is being used in optical fiber systems as bit rate increases. 128 QAM modulates 7 bits per symbol and have symbol rate of 1/7 bit rate.