I received my PhD in December, so I already pursued further education. My masters was in telecommunications, starting my PhD with a background in signal processing/information theory rather than optics/physics. All the master students I supervised either had similar background like me or an optics/physics background. That said, optical communications combines multiple disciplines, which makes it so fascinating, and I think that a PhD is inevitable if you want to pursue a career here. There are so many steps to understand to get from bits to electrical signal to optical signal and all the way back to bits. I don't think a masters degree can cover all of it in depth. Further, a PhD is in particular helpful due to the conferences where all the big players are looking out to hire you, or where one meets senior researchers for potential postdoc positions.

Salary-wise it's difficult for me to answer, as most of the big industry players are in the US or Canada, but I'm in Europe. From hearsay a fresh PhD with reasonable publication list will get around 10k per month in the bay area. However, glassdoor might give you a better idea. Look for companies like: Infinera/ciena/acacia communications/juniper/mellanox/finisar/keysight...

After my PhD, I probably could have pursued a postdoc somewhere in Europe, but I decided to leave academia. I wanted to stay in Copenhagen and therefore had to change my field of work and will be working for a hearing aid company in their signal processing department.