A novel architecture of hybrid (WDM/TDM) passive optical networks with suitable modulation format

A Review on Radio-Over-Fiber Technology-Based Integrated (Optical/Wireless) Networks

“…This is the key advantage of using it. So therefore the MZM used in intensity modulation approach should be replaced by optical PM [8]. The limitation of the above techniques is that an ultra-narrowband optical filter is required, which causes poor system stability and high cost.…”

“…The method of external modulation suffers from distortion due to the intrinsic nonlinearity of the modulators, high power consumption and complexity. Of course, this modulation system is more expensive than the direct modulation [7,8].…”

“…The desired amplitude-modulated microwave signal is generated after heterodyning. The transmitter may also use multiple LDs, and thus a multiwavelength RoF system can be realized with a tunable wavelength division multiplexing (WDM) filter to select the desired wavelength radio channel at the antenna site [8]. As phase noise is a major problem in mmwave transmission, care must be taken to produce a small phase noise only by the heterodyned signals.…”

“…As phase noise is a major problem in mmwave transmission, care must be taken to produce a small phase noise only by the heterodyned signals. This approach overcomes chromatic dispersion effect and also offers flexibility in frequency since frequencies from some megahertz up to the terahertz region are possible [7,8] (Figure 5). …”

“…This generated signal is then compared with the reference signal. A frequency error signal in the case of the OFLL (and a phase error signal in the case of OPLL) is fed back to the slave laser [8]. Hence, the slave laser is forced to track the master laser at a frequency offset corresponding to the frequency of the microwave reference oscillator.…”