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Essay: Transmitters – findings

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  • Published: 27 October 2015*
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  • Words: 167 (approx)
  • Number of pages: 1 (approx)

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1. It is shown that the transmitters on the basis of direct modulated lasers using a pump structured provide significant improvement of the quality of communication systems at 10 Gb/s in the optimization of receiver and structure of the pump signal. The conditions are found in which the transmission range using such transmitters is increased by 70% compared to systems using standard transmitters on the basis of lasers with direct modulation.
2. Found laser parameters with direct modulation, in which the transmitter it is based on the implemented encoding format, providing destructive interference between logical units separated by a logical zero. It is shown that this format is 2 times more stable and using a special optical filter is 5 times more stable to chromatic dispersion than the standard binary format.
3. Study the stability of various binary modulation formats, as well as a pseudo three-level format PSBT to polarization mode dispersion at a transmission rate of 40 Gb/s have shown that to obtain communication system with an acceptable level of quality (BER <10-9), it is necessary that the bandwidth of the receiver lying in the range 0.5 - 1.2 rate. It is shown that the amplitude-phase format with alternating polarity, as well as 4-level format of 4-ary ASK can extend this range by moving its lower bound, respectively, to 0.35 and up to 0.2 rate that, other things being equal, can be used for these formats receivers with lower bandwidth transmission. For all the above optimum values formats found receiver bandwidth in which achieved maximum DGD. 4. It is shown that the multi-level formats more stable to polarization mode dispersion than binary. Ceteris paribus format 4-ary ASK increases the allowable DGD almost 2 times in comparison with the NRZ practically at any receiver bandwidth. The maximum allowable DGD (with BER <10-9) among other binary formats was achieved using RZ format with a duty cycle of 50%, but an increase in the allowable DGD compared to them was not more than 0.5%. 5. Investigation of the stability of different modulation formats to the effects of chromatic dispersion in optical fiber lines communication at a rate 40 Gb/s have shown that the communication system using different modulation formats in different susceptible to degradation occurring due to intersymbol interference and increase of noise at the receiver with an increase of its bandwidth. It is shown Formats that PSBT, AMI and 4-ary ASK allow narrow bandwidth receiver, ceteris paribus, respectively 24%, 40% and 60% compared to the NRZ. For each format found optimal bandwidths of the receiver, at which the maximum transmission distance with a coefficient of chromatic dispersion 17 ps/nm/km. 6. Maximum transmission distance in systems operating at 40 Gb/s was achieved using the format alternating polarity (with BER<10-9). As compared with NRZ-coding, it is increased by 3.5 times. The 4-ary ASK and PSBT also showed great stability to chromatic dispersion than NRZ: using them transmissions distance increases respectively 2.5 and 1.8 times. 7. Investigation of the stability of various formats to nonlinear effects showed that the range of transmission systems at 40 Gb/s using a majority binary formats at constant chromatic dispersion of 17 ps/nm/km decreases almost linearly with an increase in the coefficient of nonlinearity. Among them, the most stability to nonlinear effects showed RZ code with a duty cycle of 33%: the increase in the nonlinearity coefficient from 0 to 30 W-1km-1, the maximum transmission distance is reduced by only 0.1%. 8. A new method of electronic dispersion compensation (EDC), which consists in the fact that the amplitude-modulated signal gets through a certain distance in the fiber modulator further phase modulation, resulting in the output of the fiber is formed an inverted signal. Electronic dispersion compensation method is called "time lens" because of the analogy with the conventional lens, arising due to the symmetry of the wave equation for the spatial and temporal coordinates. The possibility to use it to transmit information at a rate of 40 Gb/s over a distance greater than 110 km without dispersion compensating fiber, including a reconfigurable networks. 9. For the first time it provides a method of forming an amplitude-modulated signal at the output of the optical fiber communication line (FOCL) of a continuous phase modulated radiation (FAMS/CPMR). Describes one possible implementation schemes FAMS/CPMR. Method FAMS/CPMR proposed to use to transmit information. The possibility of transmitting information at a distance of over 1,700 km at speed of 40 Gb/s and BER, not more than 10-12.

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