The invention provides an
optical transmitter with a
hybrid modulation format. The
optical transmitter is applied to a passive optical
access network and a long-distance optical
transmission system, wherein the passive optical
access network is formed by integrating a
wavelength division
multiplexer and an optical branching device. The
optical transmitter comprises an I / Q modulator 1, an I / Q modulator 2, a
delay line interferometer and a Mach-Zehnder modulator. The I / Q modulator 1 is in
cascade connection with the
delay line interferometer, then is in
cascade connection with the I / Q modulator 2 and lastly, is in
cascade connection with the Mach-Zehnder modulator. The two I / Q modulators are respectively provided with two
data input ports, and the Mach-Zehnder modulator is provided with one
data input port. The optical
transmitter is controlled to output an optical
signal with the self-
adaptation hybrid modulation format by controlling the on-off and the
signal amplitude of the
data input ports and the bit and the phase position
delay of the
delay line interferometer. By means of the optical
transmitter,
QPSK modulation, 8
QAM modulation and circular 16
QAM modulation can be achieved, and
hybrid transmission formed by various modulation formats in any proportional mode can also be achieved. The optical
transmitter can be applied to complex transmission links under the
wavelength division
multiplexing passive optical network environment, and the
frequency spectrum utilization efficiency can be effectively improved.