VI Systems says it has demonstrated an 850-nm vertical cavity surface emitting laser (VCSEL) capable of transmitting 54 Gbps over 2.2 km of standard OM4 multimode fiber. The company described the demonstration in the most recent issue of the Electronics Letters publication of the Institution of Engineering and Technology (IET).
According to the company, the VCSEL design features a narrow optical spectrum at a high optical output power. VI Systems reports that it leveraged "advanced computer simulation software" as an aide to its VCSEL design work.
The VCSEL supported the 56-Gbps optical transmission using conventional non-return-to-zero (NRZ) on/off keying (OOK) modulation. Such an approach offers lower latency than more complex higher-order modulation formats also under consideration for 50-Gbps transmission, VI Systems adds.
The company didn't say so specifically, but it likely had PAM4 in mind when it made that last statement. The IEEE has made PAM4 modulation the basis of several high-speed Ethernet specifications now under development (see "IEEE sets objectives for 200 Gigabit Ethernet"). In addition to lower latency, the use of OOK likely would result in a lower-cost approach as well.
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