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Introduction
Published in Le Nguyen Binh, Advanced Digital, 2017
Current 10 Gbps transmission systems employ intensity modulation (IM), also known as on–off keying (OOK), and utilize non-return-to-zero (NRZ) pulse shapes. The term OOK can also be used interchangeably with amplitude shift keying (ASK) [1,2].* For high-bit-rate transmission such as 40 Gbps, the performance of OOK photonic transmission systems is severely degraded owing to fiber impairments, including fiber dispersion and fiber nonlinearities. The fiber dispersion is classified as CD and polarization-mode dispersion (PMD), causing the intersymbol interference (ISI) problem. On the contrary, severe deterioration in the system performance due to fiber nonlinearities result from high-power spectral components at the carrier and signal frequencies of OOK-modulated optical signals. It is also of concern that existing transmission networks comprise millions of kilometers of SSMF, which have been installed for approximately two decades. These fibers do not have as advanced properties as the state-of-the-art fibers used in recent laboratory “hero” experiments, and they have degraded after many years of use.
Binary Digital Optical Modulation
Published in Le Nguyen Binh, Optical Modulation, 2017
Current 10 Gb/s transmission systems employ intensity modulation (IM), also known as on-off keying (OOK), and utilize the non-return-to-zero (NRZ) pulse shapes. The term OOK can be used interchangeably with amplitude shift keying (ASK). It is noted here that the OOK format simply implies the on–off states of the optical lightwaves where only the manipulation of the intensity is considered. On the other hand, the ASK format takes into account not only the amplitude, but also the phase in the constellation diagram. Moving towards high bit rate transmission, the performance of OOK photonic systems is severely degraded due to fiber impairments, including fiber dispersion and fiber non-linearities. The fiber dispersion is classified into chromatic dispersion (CD) and polarization mode dispersion (PMD), causing the intersymbol interference (ISI) problem. On the other hand, severe deterioration on the performance due to fiber non-linearities are the result of the high-power spectral components at the carrier and signal frequencies of OOK-modulated optical signals. It is also of concern that existing transmission networks are comprised of millions of kilometers of SSMF, which have been installed for approximately two decades. The properties of these fibers are not only low-performance compared to the state-of-the-art fibers used in recent laboratory “hero” experiments, but have also degraded after many years of use.
Modulation, Coding, and Multiple Access
Published in Roberto Ramirez-Iniguez, Sevia M. Idrus, Ziran Sun, Optical Wireless Communications, 2008
Roberto Ramirez-Iniguez, Sevia M. Idrus, Ziran Sun
If the variations in amplitude of the carrier occur in proportion to variations in the amplitude of the modulating signal, then the modulation scheme is called ASK or on-off keying (OOK). If, on the other hand, the representation of the binary signal is carried out by shifting the phase of the sinusoidal carrier, the modulation scheme is called PSK. This is illustrated in Figure 8.6 where a binary set of data is first converted into NRZ form. The new set of data is then used to modulate a carrier using PSK as described above. If, rather than the phase or amplitude of the carrier, it is its frequency that is varied in proportion to the amplitude of the modulating signal (the binary code), then the modulation scheme is called FSK. This is illustrated in Figure 8.7. Depending on the bandwidth efficiency required in the channel bandwidth use, more complex versions of these modulation techniques can be employed at the cost of increased complexity. Examples of systems based on PSK and FSK can be found in [10, 11]. Here, Gfeller et al. shown that if the environment is diffuse and there are different paths for the transmitted energy, then PSK presents synchronization problems. For this reason (and because of its flexibility to data rate variations), FSK is preferred over PSK even if both of them present similar performances in terms of bit error rate. Another example of a system based on PSK is the 48-kbps networking system developed by Fujitsu [35] (cf. Chapter 1).
Energy optimisation of an On-Off Keying (OOK) transmitter using high-order orthogonal modulation
Published in International Journal of Electronics Letters, 2019
Yue Peng, Guillaume Andrieux, Jean-François Diouris, Magaye Diop
On-off keying (OOK) is the simplest form of amplitude-shift keying that represents digital data by the presence or absence of carrier. It has the advantage of more simple circuits than more complex modulations. A good energy efficiency can be expected if the transmitter can be switched off during the transmission of zeros. Design of efficient OOK transmitters can be found in Daly, (Chee, Niknejad, & Rabaey, 2006; Daly & Chandrakasan, 2007; Jung, Zhu, Liu, Chen, & Heo, 2010; Kuan-Hsiu & Hwann-Kaeo, 2015; Raja, Chua, & Xu, 2012; Shirai, Hirose, & Hashimoto, 2017; Yousefi, Koozekanani, Sobhi, & Azizkandi, 2014) for VHF, UHF or K-Band.