Fiber Optic Communicaiton

Communication system has three main phases:-

• Transmitter
• Transmission Media (Fiber Optic)
• Receiver

Suppose two persons are sanding at short distance. One person says something to another person by shouting. Voice travels via a medium air. When the distance is longer than, we can not transmit the voice by air only. At this time it is very necessary that we have to use some medium which could carry the sound wave along with. When transmission takes place between two devices transmitting medium is required. These transmission media are the transmission lines or communication channels.
Here we are going to introduce fiber optic Communication Fiber Optic Communication:-

Fiber Optic Communication is a technique of transmitting information from one place to another by sending light through an optical fiber. The light forms an electromagnetic carrier wave which is modulated to carry information. Fiber Optic developed in the 1970’s. Fiber optic has revolutionized the telecommunication industry and offers the advent of the information technology. In Fiber Optics, semiconductors lasers transmit information in the form of light passing through the hair thin glass fibers, with no significant loss of intensity over very long distance. Electrical signals are converted into light wave and feed to the optical fiber medium which carries the light signals to the another end and than again the light signals are converted to the electrical signals with the help of photoelectric diode. These signals are amplified and sent to the receiver.

Advantages of the optical fiber:-
Optical fiber provides high quality of transmission of signals at very high speed. Whereas in copper wire transmission it takes about one hour but in optical fiber it just took one second.
Optical fiber may be used to communicate either analog or digital signals. In analog transmission, the light intensity varied continuously but, in digital transmission the light source is tuned on and off.
Optical fiber transmission is not affected by the electromagnetic interference, by which noise and distortion are also reduced which provides the better communication.
Fiber Optic provide the security to our information which we used to transmit over the medium.
Due to all above mentioned points optical fiber is popular and growing very rapidly in the market.

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Importance of PWM in SMPS Design

Different power-supply specifications drive the need for different power-supply topologies. These different power-supply topologies require various types of PWM modes. Each PWM mode play an important role in wide variety of SMPS designs including standard, push-pull, complementary, multi-phase, current-reset, variable-phase and current-limit PWM modes.

The most common PWM mode is the standard edge-aligned PWM. In this mode flow of power controls by the ratio of the on time verses the off time. Only one of the PWM outputs per output pair is used in these Asynchronous Buck, Boost and Flyback converter circuits.

Push-pull converters are mostly used in AC/DC power supplies and DC/DC converters. The term "multiphase PWM" means multiple PWM outputs that are not edge-aligned. Multiphase converter circuits are mostly used in DC/DC converters that must supply high current in applications where the load may change very rapidly.

Our Synchronous Buck Converter uses a complementary PWM mode, where the complementary output controls a "synchronous switching" rectifier that is implemented with a MOSFET, instead of the typical rectifier. The complementary PWM mode can also be used in other circuits that use synchronous rectification to improve system efficiency.

Phase-shifted PWM mode is widely used in personal computer power supplies so that it is becoming more common mode. SMPS family supports all of the known PWM modes currently in wide use by the power-supply industry.

A pulse width modulation (PWM) generator featuring very high speed and high resolution capability and the ability to generate standard complementary PWM, push-pull PWM, variable offset PWM, multiphase PWM, current limit PWM, current reset PWM, and independent time base PWM while further providing automatic triggering for an analog-to-digital conversion (ADC) module that is precisely timed relative to the PWM signals. Applications include control of a switching power supply that requires very high speed operation to obtain high resolution at high switching frequencies, and the ability to vary the phase relationships among the PWM output signals driving the power supply power components. A single PWM duty cycle register may be used for updating all PWM generators at once to reduce the workload of a digital processor as compared to updating multiple duty cycle registers.

For more:

• NAS Knowledge Base
• Torex Knowledge Base