fibre optic cabling has a density of less than that of copper, is thinner, and typically can carry 3 orders of magnitude more data per cable than copper.
As tech level increases you go from analog serial over a low quality copper line (300 baud phone modem from 1975 anyone?) to parallel data over short distances via ribbon cable, to high speed serial over medium distances via a high quality shielded cable (1981 COAX ) Token ring 1.5 MB, to 10 base T, 100 base T, gigabit, and with fibre optic 10 gigabit and higher is possiable. Larger data streams are handled by aggregating multiple interfaces and cables. Your fibre optic trunks in the under sea cables is not one fibre it's thousands and is distrubited between hundreds of servers on both ends, which route to all of the myrid local fibre optic trunks and on to the local ISP's and from there to the end users/generators of content.
So we have the ship's computer core with fibre optic ports to the outside, it might be 1,2,4,8,16, or more based on the computer model number, each having double the number of I/O channels of the previous model. These ports feed into a router that connects to the various equipment sensors and control panels throught the ship. Civilian ships may use wireless hotspots for mobile devices to connect into the ship's systems, reducing the need for physical wiring. By defining the computer model by the number of data ports it can support we get a sense of scaling of the model's capability to handle inputs. A model 9's 512 ports could eat half of one of the under sea fibre optic cables, and clearly could manage a battleship's myrid devices and data streams.
Computer systems designed for redundancy have no single point of failure that knocks the computer systems offline, triple redundancy has no two points of failure that can knock it offline. That's two ports are required on each computer to establish double redundancy, model 0's single port can't support it. Model 1 cannot support triple redundancy, as that needs three ports. the cabling and hardware needed to do double redundancy is two times that for a single non redundant system in that every device has two data paths to it, and three data paths for triple redundancy. Military systems will route these paths through different cable runs or use different nodes to broadcast the signal. Every device needs two/three interfaces to support the level of redundacy of the ship. This does not mean there are three EMS sensors, it means that the one sensor has three data ports, if there is a 2nd or third sensor installed each of them would have the extra interfaces as well.
UPS battery systems get smaller / lighter for given power capacity as tech increases (I realize this is CT but T4's FF&S Table 224 gives you battery sizes and costs per MW/h by TL to get you into the ballpark)
One of the answers previously given is that jump space is particularly hard on ICs, and that necessitates a different structure for the computer. Some have even suggested that tubes are required to deal with jump (or the energy discharge on entry and exit).
