Coded modulation techniques in fiber optical communications. Different modulation formats used in optical communication system shashi jawla1, r. This is an introduction to the fundamentals of coherent optical modulation techniques. Noise statistics in optically preamplified dpsk receivers. The performance can be varied by varying the width of the pulses. Demodulation is defined as extracting the original informationcarrying signal from a modulated carrier wave. 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. Before we study in detail about pam lets know the concepts of. 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. 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. The advantages of using duobinary modulation in uncompensated singlemode optical fiber channel are discussed. In order to achieve multigigabit transmission projected for. 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. Represent each possible signal as a vector in a euclidean space spanned by an orthonormalbasis.
Scientech 2502, optical fiber communication trainer, fiber optics training kits, fiber optics experiments in lab, study fiber optics modulation and demodulation. Jan 30, 2017 basics of modulation and demodulation. 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 channel refers to the physical medium carrying the information signal voice, video, data etc. 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. Introduction to modulation transfer function edmund optics. Modulation types and their constellation in the system of coordinates the modulation methods can be basically divided into different categories figure 2. Restoring or recovering the message signal from the received modulated waveform that is generally corrupted by noise types of am detectors. In modern modulation and coding design, demodulation and decoding are. The changes in the carrier signal are chosen from a finite number of m alternative symbols the modulation alphabet.
Aug 20, 2017 synchronous modulation and demodulation. 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. Synchronous modulation and demodulation photo optical. Request pdf 40 gbits, 16ary 4 bitsymbol optical modulationdemodulation scheme a practical 16ary amplitudephaseshiftkeying 16apsk optical. Ee4512 analog and digital communications chapter 6 chapter 6 analog modulation and demodulation amplitude modulation pages 306309. As the resultant is a coded pulse train, this is called as pcm. 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. Kahn stanford university, 366 packard building, 350 serra mall, stanford, ca 943059515, usa. There are different types of modulation and so are demodulators.
Can plot the signal spectrum after modulation and demodulation. 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. Us5808779a optical fiber modulation and demodulation. 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. Coherent optical modulation and demodulation ieee xplore. The allfiber mzi structure for optical dpsk demodulation. 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. Light is modulated using one or more optical reflective grating and piezoelectric crystal combinations, and demodulated using an interferometer system. The principle of an optical dc chopper is illustrated in fig. Introduction in chapters 1 and 2 you studied how to apply intelligence modulation to an rfcarrier wave. Vectors and modulation cse 466 interfacing 3 spose m and n are orthogonal unit vectors. Measurement and control of residual amplitude modulation in. Sep 30, 2017 this ezed video explains modulation techniques types of modulation analog modulation digital modulation analog modulation amplitude modulation frequency modulation phase modulation.
Free space optical using different modulation techniques a. Pulse amplitude modulation is the basic form of pulse modulation. Receivers with optical machzehnder interferometer demodulation xiupu zhang, and zhenqian qu department of electrical and computer engineering, concordia university, montreal, quebec, h3g 1m8 canada tel. Modulation schemes used in fso the optical transmission system involves modulation of optical signal, its transmission, detection and demodulation. The properties of the parallel connected photo resistor are such that the device. Describe fm demodulation circuit operation for the phaseshift and gatedbeam discriminators and the ratiodetector demodulator. Detection methods for digitally modulated optical signals are classified most logically using. In the right selection the sequence can be changed on the fly even during a running measurement. Modulation enables the transfer of information on an electrical signal to a receiving device that demodulates the signal to extract the blended.
Keysight n4391a optical modulation analyzer measure with. In general, the intent of creating an optical transmission system model is important for testing optical modulation andor coding techniques, noise thresholds, etc. Free space optical using different modulation techniques. Although an inductive type transformation process is required, the output dc may be obtained without rectifying devices. Modulation for analog communication yao wang, 2006 ee3414.
Deepspace and nearearth optical communications by coded orbital angular momentum oam modulation. Understanding iq signals and quadrature modulation radio. Coherent optical receiver for linear optical phase demodulation. Spie 8904, international symposium on photoelectronic detection and imaging 20. I output power modulated laser light current modulation i th current. Digital modulation and demodulation fsk,psk,bpsk,qpsk techniques. The amplitude of the carrier remains constant phase modulation pm another form of analog modulation technique which we will not discuss. Modulation translates a signal from its baseband to the operating range of the channel. Different modulation formats used in optical communication system. A demodulator is an electronic circuit that is mainly used to recover the information content from the modulated carrier wave.
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. 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. 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. Two phase modulators can be placed in parallel using an. 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. On the contrary, demodulation is done in order to recover the original message signal from a modulated signal. Pdf format this file type includes highresolution graphics and schematics when applicable. A lot of new abbreviations for optical modulation methods have sprung up with the. 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. Synchronous modulation and demodulation photo optical modulator. Those light waves may be sent through a transparent medium as a laser beam, or contained within a fiber optic cable.
Us5808779a optical fiber modulation and demodulation system. One approach to reduce this interference, known as frequencydivision multiplexing, allocates different carrier frequencies to different users or for dif. In singlechannel efield sensing, the carrier we transmit is m, the sensed value is a, and the noise is n vectors. An optical modulator is a device which is used to modulate a beam of light. 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.
Synchronous modulation and demodulation low dc current may be transformed into a high voltage dc by simple chopper action. Optical orbital angular momentum shiftkeying communication using direct demodulation article pdf available in ieee access pp99. Multiple impairments on optical signals are time varying due to a changing environment, drift of components, and rapid reconfiguration of network paths. N4391a window to manage user and keysight provided algorithm. The signal output from a demodulator may represent sound an. Osa microringbased modulation and demodulation of dpsk. In this modulation, the signal is sampled at regular intervals and each sample is made proportional to the amplitude of the modulating signal. Different modulation formats used in optical communication.
Both modulation and demodulation are reverse processes of each other. Difference between modulation and demodulation with. Osa polarization modulation and demodulation of light. Demodulation is extracting the original informationbearing signal from a carrier wave. 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. In praxis, however, all systems are bandwidth limited. Optical modulation amplitude oma and extinction ratio. Signal demodulation an overview sciencedirect topics. Duobinary modulation is a scheme for transmitting r bitssec using less than r2 hz.
In this paper, the objective is to study the performance of different modulation formats. Depending on the parameter of a light beam which is manipulated, modulators may be categorized into amplitude modulators, phase modulators, polarization modulators etc. Describe phase demodulation circuit operation for the peak, lowpass filter, and conversion detectors. A tutorial introduction to optical modulation techniques. The modulation scheme needs to be cost efficient circuitry should be simple to implement and inexpensive e.
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. Johansson, hsufeng chou, anand ramaswamy, jonathan klamkin, larry 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. Each channel sharing scheme a set of basis vectors. Also, it should be mentioned that the perfect triangular shape of the correlation function discussed in section 11. Singh2 1ece department, jec jorhat, assam, india 2uttarakhand technical university dehradun, india abstract. Principles of communication modulation tutorialspoint.
There are many types of modulation so there are many. An optical communication system employing polarization modulationdemodulation is described. 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. 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. Modulation and demodulation medium, it would be dif.
Electrical and computer engineering department, university of california, santa barbara, california 93106, usa. The beam may be carried over free space, or propagated through an optical waveguide optical fibre. In modulation and demodulation methods of the optical differential quadrature phase shift key dqpsk and the different modulation formats including nonreturntozeronrz, returntozero rz. In fso communication systems, the intensity of an optical source is modulated to transmit signals over channel. There are two typical choices for the modulation format of the signal. Deepspace and nearearth optical communications by coded. Coherent optical receiver for linear optical phase demodulation leif a.
Coherent detection in optical fiber systems ezra ip, alan pak tao lau, daniel j. 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. Dpsk demodulator for phase shift keying modulation format transmission, demodulator is needed at receiving side. Modulation scheme for fiber optical channel with nonlinear phase noise, in proceedings of ieee global communications conference, dec. Pdf analysis modulation formats in dwdm transmission system. Modulation optimization for noncoherent optical systems core. Due to the increases in bit rates, power and number of dwdm channels, the ook format reaches its limits for optical communications. Keysight technologies m8290a optical modulation analyzer and. Microringbased nrzdpsk modulation and demodulation schemes. The term quadrature modulation refers to modulation that is based on the summation of two signals that are in quadrature.
In digital modulation, an analog carrier signal is modulated by a discrete signal. Various modulation schemes have already been used in the electrical domain during last decade, but have not been applied in optics. Wmc probability density function pdf with valid domain indicated by pwy. Converting digital or analog data in electronic form to an optical signal suitable for fiber transmission demodulation. 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. The photocurrent at the output of the photodiode is proportional to the square of the signal amplitude. High power lasers and applications, 89040c 17 september 20. Johannisson, signal statistics in fiber optical channels with dual polarization and selfphase modulation, submitted. Optical fiber communication training system trainer kit. Pdf duobinary modulation format in optical communication. Devices of this type have been used widely in infrared signal detectors, whose output is a slowly varying dc product. Digital modulation methods can be considered as digitaltoanalog conversion and the corresponding demodulation or detection as analogtodigital conversion. Linewidth influenced by phase modulation and frequency. 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.
In this paper, we combine all the optimal and nearoptimal optical demodulation receivers that have been found to date under one general class of structured receiversthe conditional pulse nulling cpn. This is further developed as delta modulation dm, which will be discussed in subsequent chapters. The optical signal can be modulated in its amplitude. Demodulation channel decoding is the corresponding process at the receiver of converting the received waveform into a. To study and perform pulse position 6 to study and perform pulse code modulation and demodulation.