That depends on whether the segregation is for EMC or safety or both.

I would have assumed that fire alarm cables are typically specified for installation within buildings, so the underground duct solution seems odd ? Would a fibre link be more appropriate? If connecting buildings etc., what about surge protection zones, and, if applicable, the effects of LPS ?

I think we'd need a little more background to help.

That depends on whether the segregation is for EMC or safety or both.

I would have assumed that fire alarm cables are typically specified for installation within buildings, so the underground duct solution seems odd ? Would a fibre link be more appropriate? If connecting buildings etc., what about surge protection zones, and, if applicable, the effects of LPS ?

I think we'd need a little more background to help.

Thanks for your response, agreed the context is a little vague, this would be a cross site distribution network, the FA cables would indeed be SWA fibres, they would also be running along side other Band 1 ELV services such as alarm and Data, and Band 2 LV. each service runs in its own buried duct with the appropriate spacing for EMC, the proposal is to have a combined access draw pit, my query is that would it be acceptable to include all of the said services particularly the FA provided the spacing is maintained, or does segregated mean separate pits ??  it would have  a very large financial impact to provided separate draw pits for effectively 1 cable !

Except for considerations of if/how you earth the armour (and, if there is one, the internal steel wire catenary wire), there is no advice for separation of optical fibre cables from other cables for EMC or basic electrical safety. I assume the earthing study for the site has addressed earthing (and/or gapping) of the armour/internal catenary?

Steven Martin said:

or does segregated mean separate pits

This is a question really aimed at whether this is classed as a Safety Service, and in fact probably is. If the fire detection and fire alarm system is classed as a safety service, there may, of course, be a consideration for protection against fire, redundancy, and diverse cable routing. This is driven by the Fire Risk Assessment and Emergency Response Plans for the site.