Sponsoredby:
ANRITSU
Evolution of signal quality analyzers to multilevel signal generation
ports, plan evolution to higher speed per port, to efficiently address their next to come business opportunities. Last but not least, the industry agrees that speed increase must be achieved together with reduced power consumption, size and cost, for any next generation networking solution. Currently facing several options (Time Division Multiplexing, M o d u l a t i o n s ,
high frequency harmonics in the generated output signal. PAM is also a potential solution for server to server and backplane high speed connections, helping increasing the bit rate of the transmitted signal to get as close as possible to 100Gbps, while keeping the symbols baud rate in the 20Gbps to 32Gbps range. To investigate PAM transmission, R&D centers, network equipment manufacturers and component/ device/chipset manufacturers have a need to generate high quality multilevel signals. Their goal is to verify whether Pulse Amplitude Modulated signals can flow through different kinds of (quite often low cost) media and still be recognized by the receiver, thus providing a cost efficient and low power consumption solution to allocate larger bandwidth to each network equipment port. To cope with this exciting trend to higher speed transmission, test and measurement companies must offer suitable high quality solutions,meeting their customers’ need to reduce effort and time required to implement their testing setups. For this reason, the most advanced Bit Error Rate Testers for R&D applications, now also known as Signal Quality Analyzers, are including multilevel signal generation as one of the newest testing capabilities. As this is a very specialized feature, it is best supported by adding dedicated modules which provide an embedded complete array of pre-set coupled connections to allow engineers to simply input multiple electrical differential signals and get an high quality electrical differential Pulse Amplitude Modulated multilevel output signal. The two most requested PAM functions are PAM4 and PAM8, respectively representing 2 bits (4 values) and 3 bits (8 values) with one transmitted symbol. In terms of efficiency, if R is the bit rate of information to be transmitted, PAM4 allows an R/2
1,000,000
100,000
10,000
1,000
100 1995 2000 2005 2010 2015 2020 Date Source: 2007 HSSG Tutorial Figure 1
By Alessandro Messina T he increasing popularity of cloud computing services, together with the fast growth of smartphones and relative data sharing bandwidth consumption, we have seen a parallel evolution towards much higher transmission speeds in the telecommunications networks and in the information technology infrastructures evolve. In a famous graphical prediction, as shown in figure 1, IEEE shows the core network transfer rates doubling every 18 months while server I/O transfer rates are doubling every 24 months. Storage and data centers, already struggling with a massive increase in number of servers and
Wavelength Division Multiplexing, Space Division Multiplexing), the industry has recently started investigating QAM (Quadrature Amplitude Modulation) and PAM (Pulse Amplitude Modulation). These two methods offer possible solutions to grow from 100Gbps to future 400Gbps and higher speeds in core networks and to get to 100Gbps in short reach connections. Figure 2 shows an example of measurement configuration for Dual DP-16QAM technology as a candidate for 400G ultra long-haul transmission. This is using a multi- channel Pulse Pattern Generator
to produce the cleanest possible original signals, testing engineers need to arrange multiple signals into couplers with a rather complex setup and time consuming manual efforts, to obtain multiple PAM signals and feed them to optical phase modulation. The quality of the resulting signal is a key factor for a correct investigation of these future transmission techniques, and there is a need to carefully select high quality passive devices (couplers, attenuators, cables) to reduce the impact from unwanted attenuations, insertion losses, reflections and loss of
MP1800A Signal Quality Analyzer
32Gbaud Waveform 4 Levels Signal
Data1 Data2
10dB 10dB
32Gbaud
Data3 Data4
128Gbps
10dB 10dB
32Gbaud
256Gbps
MU183021A 32G X 4ch PPG
32Gbaud
Data1 Data2
128Gbps
10dB 10dB
512Gbps
32Gbaud 32Gbaud
Data3 Data4
128Gbps
10dB 10dB
32Gbaud
256Gbps
MU183021A 32G X 4ch PPG
32Gbaud
128Gbps
XData1-4
32Gbaud
Figure 2 – Example Measurement Configuration for Dual DP-16QAM Technology
24 | Optical Connections 2013 | www.opticalconnectionsnews.com |
Made with FlippingBook - Online catalogs