[xhrpost]

I don't think they are terminated every Nkm anymore. We have been able for quite some time to re-energize the signal directly in the optical core without needing to convert it to electric then back.

https://en.wikipedia.org/wiki/Laser_pumping

[oakwhiz]

If a cable is long enough to require amplifiers, they are spliced in. Couplers/circulators need to be in line with the doped section of fiber that forms the laser amplifier, both before and after. One of the couplers injects the pumping beam from another laser into the doped section. This necessitates splicing at every amplifier. Also, almost every strand in the cable would require amplification.

In addition there are feedback, failover and monitoring functions that require more optical components to be included, and it's likely that this type of functionality will increase as demand for improved latency and reliability increases, and new cable networks are built.