Microsoft PowerPoint fiberoptic [Compatibility Mode]
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= Dispersion coefficient (psec/km-nm) L = Distance (km) T = bit interval (psec) λ ∆ = Spectrum width (nm) Optical Optical Source and Detectors Source and Detectors’ ’ Sensitivity Sensitivity The spectral width of an optical source is commonly specified as the fullwidth at half-maximum (FWHM) which represents the spread between the wavelength at which the spectrum is at half the magnitude of the peak. The receiver sensitivity decreases with data rate. Prof. Murat Torlak EE4367 Telecom. Switching & Transmission Change in Sensitivity R = ∆ 10 log 10 (R 0 /R) where R = new data rate R 0 = reference data rate 0 10 0 Sensitivity Sensitivity 10 log R R R R = + Optical Transmission System Design Optical Transmission System Design Transducers Electrical-to-optical Prof. Murat Torlak EE4367 Telecom. Switching & Transmission Spectral with of an optical source is commonly specified as the full width at half-maximum (FWHM) Optical-to-Electrical Line Coding in Optical Transmission Line Coding in Optical Transmission Some fiber systems use the line codes described for wireline transmission that we studied previously. A few line codes are specifically developed for fiber applications. Note that optical sources and detectors are primarily used in nonlinear modes of operation with significant gain and threshold variations. Prof. Murat Torlak EE4367 Telecom. Switching & Transmission threshold variations. They are best suited for on or off. On-off keying is most natural for optical transmissions mBnB Line Codes mBnB Line Codes mBnB – codes m binary bits into n bits (m from the set of thirty-two 5-bit line codes. This is 4B5B line code. The code space is used for control as well as data. When transmitting data, the minimum pulse density is 40% and there can never be more than three intervals without a Prof. Murat Torlak EE4367 Telecom. Switching & Transmission and there can never be more than three intervals without a pulse 8B10B coding is used for fiber optics transmission Each input byte is separated into a 5-bit filed and a 3-bit field that respectively encoded using a 5B6B and 3B4B algorithm. Other Line Code Examples Other Line Code Examples Digital Biphase (Manchester) 1B2B line code Coded Mark Inversion (CMI) 1B2B Line Code Prof. Murat Torlak EE4367 Telecom. Switching & Transmission Bit Insertion Codes mB1P code inserts an odd parity every m bits of input mB1C inserts a bit after every m source bits, complementary to preceding pulse value. Performance cannot be monitored. WDM WDM Achieved through refraction and diffraction technique for combining and separating optical signals of different wave lengths. Dense Wave Division Multiplexing Closely spaced wavelengths are used. Prof. Murat Torlak EE4367 Telecom. Switching & Transmission Closely spaced wavelengths are used. The current methods are: Thin-film filters Arrayed Wavelengths Diffraction Grating WDM WDM WDM is fundamentally identical to frequency division multiplexing as used on electrical or radio transmission systems. In fact, using the following relationship allows wavelengths to be related to frequency Yüklə 92,45 Kb. Dostları ilə paylaş:
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