In optical networking, NRZ refers to Non-Return-to-Zero. A binary modulation format using two signal levels, historically common in 1G through 100G optical interfaces. Engineers commonly encounter it while planning or operating Legacy and lower-speed optical links.
The reference framework matters when specifying NRZ for Legacy and lower-speed optical links. Values should be read from the product data sheet together with the measurement method and the limits required by IEEE, ITU-T, or the applicable MSA. A product name or quotation that mentions NRZ without that context is not yet a complete requirement.
NRZ should not be treated as another name for PAM4. NRZ is defined here as a binary modulation format using two signal levels, historically common in 1G through 100G optical interfaces. By comparison, PAM4 means a modulation format encoding two bits in each symbol using four amplitude levels, enabling higher data rates per lane. The two concepts may appear in the same design, but they answer different engineering or purchasing questions.
For a deployable NRZ requirement, record test wavelength, temperature, pattern, data rate, reference receiver, measurement uncertainty, and guaranteed limits. Do not infer those details from Rx Sensitivity or from a headline speed alone, because the related concept is defined separately as the minimum received optical power at which a receiver can meet the required bit error performance.
Frequently Asked Questions
Are NRZ and PAM4 interchangeable?
No. NRZ describes a binary modulation format using two signal levels, historically common in 1G through 100G optical interfaces, while PAM4 describes a modulation format encoding two bits in each symbol using four amplitude levels, enabling higher data rates per lane. Confirm both separately when the design uses both concepts.
Where is NRZ normally used?
Typical use includes Legacy and lower-speed optical links. The exact implementation still depends on the host equipment, link design, environment, and governing specification.
What should a NRZ specification include?
It should state test wavelength, temperature, pattern, data rate, reference receiver, measurement uncertainty, and guaranteed limits. These details allow a supplier or engineer to verify the requirement instead of relying only on the term NRZ.
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