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Optical Communications & Networks (ECE 401) : Topic: Dual Polarisation Quadrature Amplitude Modulation

1) Quadrature amplitude modulation (QAM) conveys two digital bit streams or analog message signals using amplitude-shift keying and amplitude modulation by modulating the amplitude of two sinusoidal carrier waves that are 90 degrees out of phase. 2) QAM is a combination of both phase-shift keying and amplitude-shift keying and is widely used in digital telecommunication systems to achieve high spectral efficiencies. 3) The document discusses using QAM with dual polarization to analyze performance for different bit rates from 10Gbps to 1Tbps over varying optical fiber lengths from 10km to 130km by observing constellation diagrams.

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Ram Gopal Vetukuri
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63 views3 pages

Optical Communications & Networks (ECE 401) : Topic: Dual Polarisation Quadrature Amplitude Modulation

1) Quadrature amplitude modulation (QAM) conveys two digital bit streams or analog message signals using amplitude-shift keying and amplitude modulation by modulating the amplitude of two sinusoidal carrier waves that are 90 degrees out of phase. 2) QAM is a combination of both phase-shift keying and amplitude-shift keying and is widely used in digital telecommunication systems to achieve high spectral efficiencies. 3) The document discusses using QAM with dual polarization to analyze performance for different bit rates from 10Gbps to 1Tbps over varying optical fiber lengths from 10km to 130km by observing constellation diagrams.

Uploaded by

Ram Gopal Vetukuri
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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OPTICAL COMMUNICATIONS

NETWORKS

&

(ECE 401)

TOPIC : DUAL POLARISATION


QUADRATURE AMPLITUDE MODULATION

Submitted to: Jabeena A

Submitted by :
Ram gopal
V(13BEC0848)

Murali Krishna M
(13BEC0288)
Slot: B1+TB1

Quadrature amplitude modulation (QAM) is both an analog


and a digital modulation scheme. It conveys two analog
message
signals,
or
two
digital bit
streams,
using
the amplitude-shift keying (ASK) digital modulation scheme
or amplitude modulation (AM) analog modulation scheme. The
two carrier waves of the same frequency, usually sinusoids,
are out of phase with each other by 90 and are thus
called quadrature carriers or quadrature components. The
modulated waves are summed, and the final waveform is a
combination of both phase-shift keying (PSK) and amplitudeshift keying (ASK), or, in the analog case, of phase modulation
(PM) and amplitude modulation. In the digital QAM case, a finite
number of at least two phases and at least two amplitudes are
used. PSK modulators are often designed using the QAM
principle, but are not considered as QAM since the amplitude of
the modulated carrier signal is constant. QAM is used
extensively
as
a
modulation
scheme
for
digital telecommunication systems. Arbitrarily high spectral
efficiencies can be achieved with QAM by setting a suitable
constellation size, limited only by the noise level and linearity
of the communications channel. Like all modulation schemes,
QAM conveys data by changing some aspect of a carrier signal,
or the carrier wave, (usually a sinusoid) in response to a data
signal. In the case of QAM, the amplitude of two waves of the
same frequency, 90 out-of-phase with each other (in
quadrature) are changed (modulated or keyed) to represent the
data signal. Amplitude modulating two carriers in quadrature
can be equivalently viewed as both amplitude modulating and
phase modulating a single carrier.

COMPONENTS REQUIRED:

CW LASER, LiNb Mach-Zender Modulator, Single Mode Optical


Fiber, EDFA, Photo detectors PIN, Low Pass Bessel Filter.

We will analyze the performance for different bit rates (10gbps1Tbps) and for different optical fiber lengths ( ranging 10km130km) and the constellation diagram will be observed.

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