Optical modulation and demodulation pdf

Modulation types and their constellation in the system of coordinates the modulation methods can be basically divided into different categories figure 2. Demodulation is extracting the original informationbearing signal from a carrier wave. There are many types of modulation so there are many. Pdf duobinary modulation format in optical communication. Restoring or recovering the message signal from the received modulated waveform that is generally corrupted by noise types of am detectors. Singh2 1ece department, jec jorhat, assam, india 2uttarakhand technical university dehradun, india abstract. Linewidth influenced by phase modulation and frequency.

Moreover, the fiber impairments depend on complex interactions of linear and nonlinear fiber effects, which in turn are a function of the signal power, data rate, and data modulation format. A tutorial introduction to optical modulation techniques. Electrical and computer engineering department, university of california, santa barbara, california 93106, usa. The term quadrature modulation refers to modulation that is based on the summation of two signals that are in quadrature. Kahn stanford university, 366 packard building, 350 serra mall, stanford, ca 943059515, usa. A demodulator is an electronic circuit or computer program in a softwaredefined radio that is used to recover the information content from the modulated carrier wave. This is further developed as delta modulation dm, which will be discussed in subsequent chapters. Modulation optimization for noncoherent optical systems core.

On the contrary, demodulation is done in order to recover the original message signal from a modulated signal. Spie 8904, international symposium on photoelectronic detection and imaging 20. Deepspace and nearearth optical communications by coded. Jan 30, 2017 basics of modulation and demodulation. Light is modulated using one or more optical reflective grating and piezoelectric crystal combinations, and demodulated using an interferometer system. The allfiber mzi structure for optical dpsk demodulation. Digital modulation and demodulation fsk,psk,bpsk,qpsk techniques. Wmc probability density function pdf with valid domain indicated by pwy. Request pdf 40 gbits, 16ary 4 bitsymbol optical modulationdemodulation scheme a practical 16ary amplitudephaseshiftkeying 16apsk optical. Pdf analysis modulation formats in dwdm transmission system. The signal output from a demodulator may represent sound an. The first step in the design of an optical communication systems is to decide how the electrical signal should be converted into an bit stream. Both modulation and demodulation are reverse processes of each other.

Converting digital or analog data in electronic form to an optical signal suitable for fiber transmission demodulation. Represent each possible signal as a vector in a euclidean space spanned by an orthonormalbasis. Digital modulation methods can be considered as digitaltoanalog conversion and the corresponding demodulation or detection as analogtodigital conversion. Different modulation formats used in optical communication system shashi jawla1, r. In the right selection the sequence can be changed on the fly even during a running measurement. As the resultant is a coded pulse train, this is called as pcm. Dpsk demodulator for phase shift keying modulation format transmission, demodulator is needed at receiving side.

This results in loss of phase information, and is therefore unsuitable for advanced modulation formats that use the phase dimension to. Each channel sharing scheme a set of basis vectors. Dpsk is widely used for long haul and untra lh transmission and the required demodulator at receiving is relatively simple, namely just need to split the signal into two and delay one bit period in one optical path. Pulse amplitude modulation is the basic form of pulse modulation. Those light waves may be sent through a transparent medium as a laser beam, or contained within a fiber optic cable. Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. The photocurrent at the output of the photodiode is proportional to the square of the signal amplitude. In modulation and demodulation methods of the optical differential quadrature phase shift key dqpsk and the different modulation formats including nonreturntozeronrz, returntozero rz. The channel refers to the physical medium carrying the information signal voice, video, data etc. To study and perform pulse position 6 to study and perform pulse code modulation and demodulation. The performance can be varied by varying the width of the pulses. The modulation scheme needs to be cost efficient circuitry should be simple to implement and inexpensive e. In this paper, the objective is to study the performance of different modulation formats. Synchronous modulation and demodulation low dc current may be transformed into a high voltage dc by simple chopper action.

Various modulation schemes have already been used in the electrical domain during last decade, but have not been applied in optics. Ee4512 analog and digital communications chapter 6 the dsbsc am coherent receiver has a bandpass filter centered at f c and with a bandwidth of twice the bandwidth of st because of the lsb and usb. Detection methods for digitally modulated optical signals are classified most logically using. Optical modulation a tutorial introduction to optical modulation techniques by gary breed editorial director t his article introduces the subject of optical modulation, the process of applying information to a light wave. Pdf format this file type includes highresolution graphics and schematics when applicable. Introduction to modulation transfer function edmund optics. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a. The major difference between modulation and demodulation is that modulation is the act of altering the parameters of the carrier signal according to message signal for convenient data transmission. Although an inductive type transformation process is required, the output dc may be obtained without rectifying devices. Ook amplitude modulation and optical dual binary odb modulation can only be used in a very restricted sense for 4043 gbps for the reasons described above. Understand the principle of amplitude modulation know how to modulate a signal to a certain frequency know how to demodulate a signal back to the baseband can write the equation and draw block diagram for both modulation and demodulation can plot the signal spectrum after modulation and demodulation. Duobinary modulation is a scheme for transmitting r bitssec using less than r2 hz. Modulation and demodulation introduction a communication system that sends information between two locations consists of a transmitter, channel, and receiver as illustrated in figure 1.

Coherent optical receiver for linear optical phase demodulation leif a. Measurement and control of residual amplitude modulation in. In this modulation, the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the modulating signal. Optical orbital angular momentum shiftkeying communication using direct demodulation article pdf available in ieee access pp99. The system offers significant improvements in usable transmitted power or extended range, lessened susceptibility to interference from linearly polarized background light, and ease of transmitterreceiver alignment over the performance of a comparable intensitymodulated optical communication system. Coded modulation techniques in fiber optical communications. A complete and comprehensive reference on modulation and signal processing for visible light communication this informative new book on stateoftheart visible light communication vlc provides, for the first time, a systematical and advanced treatment of modulation and signal processing for vlc. Osa polarization modulation and demodulation of light. Kikuchi, coherent detection of phaseshift keying signals using digital carrierphase estimation, in proceedings of ieee conference on optical fiber communications, institute of electrical and electronics engineers, anaheim, 2006, paper otui4. Information can be sent from a transmitter to a receiver by means of modulation and demodulation, respectively, whether those signals are light waves moving through optical cables. In modern modulation and coding design, demodulation and decoding are. Also, it should be mentioned that the perfect triangular shape of the correlation function discussed in section 11. Modulation is a process through which audio, video, image or text information is added to an electrical or optical carrier signal to be transmitted over a telecommunication or electronic medium.

Optical fiber communication training system trainer kit. Before we study in detail about pam lets know the concepts of. Optical modulation amplitude oma and extinction ratio. The advantages of using duobinary modulation in uncompensated singlemode optical fiber channel are discussed. The changes in the carrier signal are chosen from a finite number of m alternative symbols the modulation alphabet. Describe fm demodulation circuit operation for the phaseshift and gatedbeam discriminators and the ratiodetector demodulator. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. Multiple impairments on optical signals are time varying due to a changing environment, drift of components, and rapid reconfiguration of network paths.

This invention is directed toward a fiber optic modulation and demodulation system, and more particularly directed toward a telemetry system for relaying signals from sensors in remote, harsh environments. In order to achieve multigigabit transmission projected for. Principles of communication modulation tutorialspoint. Well use qpsk as an example of how quadrature modulation works, and in the process well see how amplitude modulation of iq signals can produce phase shifts. Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. Aug 20, 2017 synchronous modulation and demodulation. Scientech 2502, optical fiber communication trainer, fiber optics training kits, fiber optics experiments in lab, study fiber optics modulation and demodulation.

Sep 30, 2017 this ezed video explains modulation techniques types of modulation analog modulation digital modulation analog modulation amplitude modulation frequency modulation phase modulation. Noise statistics in optically preamplified dpsk receivers. Microringbased nrzdpsk modulation and demodulation schemes. Understanding iq signals and quadrature modulation radio. In fso communication systems, the intensity of an optical source is modulated to transmit signals over channel. Can plot the signal spectrum after modulation and demodulation. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. Information can be sent from a transmitter to a receiver by means of modulation and demodulation, respectively, whether those signals are light waves moving through optical cables, radio waves through metallic cables, or radio waves propagating through the air. This is an introduction to the fundamentals of coherent optical modulation techniques. The beam may be carried over free space, or propagated through an optical waveguide optical fibre. Modulation enables the transfer of information on an electrical signal to a receiving device that demodulates the signal to extract the blended. There are two typical choices for the modulation format of the signal. Modulation scheme for fiber optical channel with nonlinear phase noise, in proceedings of ieee global communications conference, dec.

Modulation for analog communication yao wang, 2006 ee3414. Different modulation formats used in optical communication. High power lasers and applications, 89040c 17 september 20. In general, the intent of creating an optical transmission system model is important for testing optical modulation andor coding techniques, noise thresholds, etc. Modulation and signal processing offers a practical guide to. Keysight n4391a optical modulation analyzer measure with. An optical modulator is a device which is used to modulate a beam of light.

This is the technique called pulse width modulation pwm which is in use since a long time for controlling motor speed and other similar inertial machineries. Modulation translates a signal from its baseband to the operating range of the channel. If the received carrier phase is assumed to be constant, each of the seven reference values will have to be shifted only once at the beginning of the simulation. Vectors and modulation cse 466 interfacing 3 spose m and n are orthogonal unit vectors. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave. Free space optical using different modulation techniques a. In praxis, however, all systems are bandwidth limited. Frequency modulation fm frequency modulation is the process of varying the frequency of a carrier wave in proportion to the amplitude of a baseband signal. A burst power when used other than the continuous power can save the total power supplied to an inertial load while achieving the same performance from the device. An optical communication system employing polarization modulationdemodulation is described. Two phase modulators can be placed in parallel using an. Devices of this type have been used widely in infrared signal detectors, whose output is a slowly varying dc product.

There are different types of modulation and so are demodulators. Signal demodulation an overview sciencedirect topics. Ee4512 analog and digital communications chapter 6 chapter 6 analog modulation and demodulation amplitude modulation pages 306309. Then inner products dot products are 1 1 0 can interpret inner product as projection of vector 1 v1 onto vector 2 v2in other words, inner product of v1 and v2 tells us how much of vector 1 is there in the direction of vector 2. The optical signal can be modulated in its amplitude. Deepspace and nearearth optical communications by coded orbital angular momentum oam modulation. Coherent optical receiver for linear optical phase demodulation. Free space optical using different modulation techniques. Modulation schemes used in fso the optical transmission system involves modulation of optical signal, its transmission, detection and demodulation. Johansson, hsufeng chou, anand ramaswamy, jonathan klamkin, larry a.

I output power modulated laser light current modulation i th current. Review of scientific instruments 83, 043111 2012 measurement and control of residual amplitude modulation in optical phase modulation liufeng li, 1,2fang liu, chun wang, and lisheng chen1,3,4,a. The principle of an optical dc chopper is illustrated in fig. One approach to reduce this interference, known as frequencydivision multiplexing, allocates different carrier frequencies to different users or for dif. In digital modulation, the modulation technique used is pulse code modulation pcm where the analog signal is converted into digital form of 1s and 0s. Us5808779a optical fiber modulation and demodulation system. Osa microringbased modulation and demodulation of dpsk. Pdf download jan 30, 2017 information can be sent from a transmitter to a receiver by means of modulation and demodulation, respectively, whether those signals are light waves moving through optical cables, radio waves through metallic cables, or radio waves propagating through the air.

A lot of new abbreviations for optical modulation methods have sprung up with the. Keysight technologies m8290a optical modulation analyzer and. Different modulation formats used in optical communication system. Difference between modulation and demodulation with.

Hongying wang, xiaoxia zhao, zhen cheng, shuli li, bianlian zhang, and yuanyuan li linewidth influenced by phase modulation and frequency modulation in optical feedback diode laser, proc. Synchronous modulation and demodulation photo optical. The properties of the parallel connected photo resistor are such that the device. Everything you need to know about coherent optical modulation.

Modulation and demodulation medium, it would be dif. Us5808779a optical fiber modulation and demodulation. Due to the increases in bit rates, power and number of dwdm channels, the ook format reaches its limits for optical communications. Synchronous modulation and demodulation photo optical modulator. Johannisson, signal statistics in fiber optical channels with dual polarization and selfphase modulation, submitted. The amplitude of the carrier remains constant phase modulation pm another form of analog modulation technique which we will not discuss. Coherent optical modulation and demodulation ieee xplore.