Where does Routing and Switching come to play here? What about PONs and plugs and such?
In: Engineering
Optical network engineer handles optical networks, most of the time it’s just maintaining the existing network, installing equipment, sometimes troubleshooting (quite rare, as most problems are on the higher layer and handled elsewhere) or replacing old devices (they pretty much last forever until outdated), and very rarely designing and setting up new networks (very rare because normally once setup the capacity is large enough to handle years of growth).
Normally Cisco just sells the necessary tools and trains the engineers to use them, they’re not involved in the setup of the actual network unless a customized product is required (ie, very niche case or very large scale). Even if a company doesn’t have the manpower, they’ll just get directed to third-party consultants.
Submarine cables are for connecting islands and continents, modern submarine cables use fiber optics. Fiber optics is also the current choice for connecting homes and offices to the ISP. Ethernet cable is the default for indoor use, connecting servers and computers in a fixed setting. Wi-Fi is mostly indoors for the last few meters to the user’s portable device or when a cable isn’t practical, though it’s sometimes used outdoors where laying a cable or installing a BTS is considered too expensive.
For end users wifi and ethernet cable connect their device to the router, which in turn normally uses fiber optic to connect to the ISP (obviously mobile ISPs use 4G/5G, and even more niche ISPs use their satellite link), which connect to each other through fiber optic. ISPs basically have an agreement (mostly paid) to allow other ISPs to access their customer’s network. That is the internet.
Hosts (servers, computers, phones, smart speakers etc) connect to each other in a network through a switch. Switches connect to each other with routers. The box from the ISP you call router has a built-in switch to allow multiple devices to connect, and use its routing component to decide if a packet is supposed to be sent to other devices in the network or to the ISP.
PON is how ISPs handle the fiber optic link to multiple customers, they only need one link from their office and split it on the last few miles to serve roughly a neighborhood. Since these subscribers share the same link, very active users might slow down the rest, which is partly why some have data caps to discourage them (good planning should have way more bandwidth than required normally, and the main reason is just to upsell the more expensive plan) and why sometimes the technician need to move or install additional splitter when an area grow (the cable themselves are usually buried with already far more links ever required for years since they are very cheap compared to the installation cost).
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