project maker
08-08-2014, 02:24 PM
OPTICAL MODULATOR
[attachment=66753]
ABSTRACT:
Optical modulator is the device which is used to modulate a beam of light. The beam may be propagated over free space or optical waveguide. In an optical communication system an electrical signal is converted to an optical signal by modulating the source of light. Optical modulator has several advantages like they reduces the undesired and unwanted effect on signal, inducing practically zero pulse dispersion.
. INTRODUCTION:
External modulation is primarily used in telecommunication system for more efficient operation at higher data rates. The optical modulation technique evolved step by step. In early 1922,Brillouin predicted light differencing by acoustic wave. Raman and Nath were analyzed acousto-optic wave in later 1937.Further there was invention of laser beam was lead to development of optical modulator technology.
To obtain modulation of intensity of a light beam is to modulate current driving the light source eg. Laser diode. This sort of modulation is called direct modulation; as opposed to external modulation performed by light modulator, therefore this light modulator is called external light modulator. With laser diode, where narrow line width is required, direct modulation is avoided due to high bandwidth chirping (linear change in frequency over time) effect and removing current to laser.
Electro-optic modulator-
It is an optical device in which a signal controlled element displaying electro-optic effect is used to modulate the beam of light. It is a subtype of refractive modulator. Electro-optic effect states that there is change in refractive index when an electric field is applied. Simplest kind of Electro-optic modulator consist of a crystal such as lithium niobate(LiNbO3) whose refractive index is a function of the strength of local electric field.
INTRODUCTION:
Absorption coefficient can be manipulated by Franz-Keldysh effect, Quantum-confined stark effect, changes in Fermi level. Usually if several such effects appear together, the modulator is called electro-absorptive modulator.
It allowed longer transmission distance with a minimum degree of pulse broadening (chirping). The device is intended for long distance optical transmissions applications (600km)
And can be used for 2.5 Gb/s or 10Gb/s bit rates with the addition of an integrated driver circuit. Electro-absorption modulated laser(EML) modules are designed to operate at the 1550 nm wavelength window. Lucent technologies E2500 series EML module requires forward current levels based on application between 50mA and 100mA below or above the current limits, the device will not perform the way it was intended to.
CONCLUSION:
This article present the brief overview of optical modulator. In this, the need for external modulation in high speed optical communication system was identified
[attachment=66753]
ABSTRACT:
Optical modulator is the device which is used to modulate a beam of light. The beam may be propagated over free space or optical waveguide. In an optical communication system an electrical signal is converted to an optical signal by modulating the source of light. Optical modulator has several advantages like they reduces the undesired and unwanted effect on signal, inducing practically zero pulse dispersion.
. INTRODUCTION:
External modulation is primarily used in telecommunication system for more efficient operation at higher data rates. The optical modulation technique evolved step by step. In early 1922,Brillouin predicted light differencing by acoustic wave. Raman and Nath were analyzed acousto-optic wave in later 1937.Further there was invention of laser beam was lead to development of optical modulator technology.
To obtain modulation of intensity of a light beam is to modulate current driving the light source eg. Laser diode. This sort of modulation is called direct modulation; as opposed to external modulation performed by light modulator, therefore this light modulator is called external light modulator. With laser diode, where narrow line width is required, direct modulation is avoided due to high bandwidth chirping (linear change in frequency over time) effect and removing current to laser.
Electro-optic modulator-
It is an optical device in which a signal controlled element displaying electro-optic effect is used to modulate the beam of light. It is a subtype of refractive modulator. Electro-optic effect states that there is change in refractive index when an electric field is applied. Simplest kind of Electro-optic modulator consist of a crystal such as lithium niobate(LiNbO3) whose refractive index is a function of the strength of local electric field.
INTRODUCTION:
Absorption coefficient can be manipulated by Franz-Keldysh effect, Quantum-confined stark effect, changes in Fermi level. Usually if several such effects appear together, the modulator is called electro-absorptive modulator.
It allowed longer transmission distance with a minimum degree of pulse broadening (chirping). The device is intended for long distance optical transmissions applications (600km)
And can be used for 2.5 Gb/s or 10Gb/s bit rates with the addition of an integrated driver circuit. Electro-absorption modulated laser(EML) modules are designed to operate at the 1550 nm wavelength window. Lucent technologies E2500 series EML module requires forward current levels based on application between 50mA and 100mA below or above the current limits, the device will not perform the way it was intended to.
CONCLUSION:
This article present the brief overview of optical modulator. In this, the need for external modulation in high speed optical communication system was identified