ITU-T G.664 PDF

This Recommendation provides guidelines and requirements for techniques to enable optically safe working conditions (for the human eye and skin) on optical interfaces of the optical transport network, including conventional synchronous digital hierarchy (SDH) systems, for equipment in both restricted and controlled locations.

The actual definition and specification of optically safe levels are considered outside the scope of this Recommendation (they are provided by IEC).

The main fields of application are systems designed for the optical transport network employing Raman amplification and dense wavelength division multiplexing (DWDM) systems with large channel counts. For the purpose of ease of operating these systems, this Recommendation focuses on automatic power reduction (APR) techniques with automatic restart.

As backwards compatibility with earlier Recommendations on the subject of optical safety is desired, this Recommendation provides some descriptions for safety procedures in the case of single and multichannel SDH systems with and without line amplifiers. Clarification is given to why procedures employing restart pulses for automatic laser shut-down (ALS) and automatic power shut-down (APSD), defined in a previous version of this Recommendation, are no longer appropriate or necessary for applications given in [ITU-T G.691], [ITU-T G.693], [ITU-T G.695], [ITU-T G.957] and [ITU-T G.959.1].

The impact of bidirectional transmission as described in [ITU-T G.692] has also been considered.

Some references are provided for keeping fibres damage-free when being operated at high optical power levels.