Có 40+ tài liệu thuộc chủ đề "kiến trúc mạng quang"
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Figure 3.38 Distributed Raman amplifier using a backward propagating pump, shown operating along with discrete erbium-doped fiber amplifiers.. In the lumped case, the Raman amplifier consists of a sufficiently long spool of fiber along with the appropriate pump lasers in a package. In the distributed case, the fiber can simply be the fiber span of interest, with the pump attached...
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Thus this wavelength gets preferentially amplified at the expense of the other wavelengths. By suitable design of the device, this effect can be used to suppress all other longitudinal modes so that the laser oscillates in a single-longitudinal mode whose wavelength is equal to twice the corrugation period. By varying the corrugation period at the time of fabrication, different operating...
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Figure 3.51 Structure of a tunable micro-electro-mechanical vertical cavity surface- emitting laser (MEM-VCSEL) (from [Vak99]).. wavelength can be changed. This is a slow method of tuning since the tilt and posi- tion of the diffraction grating have to be changed by mechanical means. However, a very wide tuning range of about 100 nm can be obtained for semiconductor lasers by...
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Figure 3.59 A lithium niobate external modulator using a Mach-Zehnder interferom- eter (MZI) configuration. modulator uses a material such that under normal conditions, its band gap is higher than the photon energy of the incident light signal. Applying an electric field to the modulator results in shrinking the band gap of the material, causing the incident photons to be absorbed...
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Application Switching Time Required Number of Ports. possible, and based on the scheme used, the number of switch ports needed may vary from two ports to several hundreds to thousands of ports when used in a wavelength crossconnect.. In this case, the switching time must be a small fraction of the bit duration. In addition to the switching time and...
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Figure 3.71 A two-state pop-up MEMS mirror, from [LGT98], shown in the popped-up position. The mirror can be moved to fold flat in its other position.. Figure 3.72 An analog beam steering mirror. The mirror can be freely rotated on two axes to deflect an incident light beam.. This mirror can be controlled in an analog fashion to realize a...
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The input signal power must be high (around 0 dBm) so that the amplifier is saturated enough to produce a good variation in gain. Moreover, as the carrier density within the SOA varies, it changes the refractive index as well, which in turn affects the phase of the probe and creates a large amount of pulse distortion.. The same phase-change...
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Figure 3.82 A four-channel add/drop multiplexer architecture.. One possible way to do this is to cascade four add/drop elements of the type shown in Figure 3.14 in series. Which of the two would you prefer from a loss perspective?. Which of the two preceding architectures would you prefer from a cost point of view?. assume that two fiber Bragg gratings...
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encoded by the presence of a light pulse in the bit interval or by turning a light source (laser or LED) "on.". A 0 bit is encoded (ideally) by the absence of a light pulse in the bit interval or by turning a light source "off.". The bit interval is the interval of time available for the transmission of a...
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Recent work to quantify the spectral efficiency, taking into account mostly cross-phase modulation [Sta99, MS00], shows that the achievable efficiencies are of the order of 3-5 b/s/Hz. Figure 4.5 shows the block diagram of a receiver. Figure 4.6 Eye diagram. (a) A typical received waveform along with the bit boundaries.. (b) The received waveform of (a), wrapped around itself, on...
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The Q function can be numerically evaluated. However, many of the simpler receivers do not have a variable threshold adjustment and set their threshold corresponding to the average received current level, namely, (I1 4_. We can use (4.14) to evaluate the BER when the received signal powers for a 0 bit and a 1 bit and the noise statistics are...
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However, codes with substantial coding gains, that is, which decrease the BER substantially for the same transmit power as in the uncoded system, have been designed by mathematicians and communication engineers over the last 50 years.. In the next section, we discuss a popular and powerful family of such codes called Reed-Solomon codes.. 4.5.1 Reed-Solomon Codes. A Reed-Solomon code, named...
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S/N and error-rate performance of A1GaAs semiconductor laser preamplifier and linear repeater systems. Reprint of the originial 1965 edition.. Noise and error-rate performance of semiconductor laser amplifiers in PCM-IM transmission systems. To this end, we will understand the various impairments that we must deal with, how to allocate margins for each of these impairments, how to reduce the effect of...
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A power amplifier is used after a transmitter to increase the output power. A line amplifier is used typically in the middle of the link to compensate for link losses. The design of the amplifier depends on the configuration. Unfortunately, the amplifier is not a perfect device. Second, the gain of the amplifier depends on the total input power. For...
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Figure 5.9 Sources of intrachannel crosstalk. (a) A cascaded wavelength demultiplexer and a mul- tiplexer, and (b) an optical switch.. The crosstalk penalty is highest when the state of polarization (SOP) of the crosstalk signal is the same as the SOP of the desired signal. Similarly, the crosstalk penalty is highest when the crosstalk signal is exactly out of phase...
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c e spectral width. NRZ modulation with spectral width. Figure 5.19 Chromatic dispersion limits on the distance and bit rate for transmission over standard single-mode fiber with a chromatic dispersion value of D. A chromatic dispersion penalty of 2 dB has been assumed in the NRZ case. this implies that the rms width of the dispersion-broadened pulse must lie within...
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The origin of PMD lies in the fact that different polarizations travel with different group velocities because of the ellipticity of the fiber core. Moreover, the distribution of signal energy over the different state of polarizations (SOPs) changes slowly with time, for example, because of changes in the ambient temperature. In addition to the fiber itself, PMD can arise from...
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To quantify the power penalty due to four-wave mixing, we will use the results of the analysis from [SBW87, SNIA90, TCF+95, OSYZ95]. This equation assumes a link of length L without any loss and chromatic dispersion.. Here Pi, Pj, and P~ denote the powers of the mixing waves and Pijk the power of the resulting new wave. In a real...
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DM soliton (5120 km). Figure 5.33 Typical contours of constant BER for a DM soliton and an NRZ modulated 10 Gb/s system. Another important factor influencing the performance of DM soliton systems is the peak-to-peak variation of the chromatic dispersion from the average over the span. In Figure 5.33, the peak-to-peak variation was chosen to be small (1.6 ps/nm-km), and...
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(a) You have a transmitter that operates at a wavelength of 1.55/~m, has a spec- tral width of I nm, and an output power of 0.5 mW. What is the length of the longest link that you can build?. (b) You have another transmitter that operates at a wavelength of 1.3/zm, has a spectral width of 2 nm, and an...