What kind of cable is used to transmit signal from flight control computers to actuators?
ARINC 629

From The Avionics Handbook, chapter 11, Boeing B-777, Fly-By-
Wire Flight Controls:


  The ACEs [Actuator Control Electronics] and PFCs [Primary Flight
  Computer] communicate with each other, as well as with all other
  systems on the airplane, via triplex, bi-directional ARINC 629 Flight
  Controls data busses, referred to as L, C, and R. The connection from
  these electronic units to each of the data busses is via a stub cable
  and an ARINC 629 coupler. Each coupler may be removed and replaced
  without disturbing the integrity of the data bus itself.


Triplex, bi-directional ARINC 629 Flight Controls data busses

Triple: The B777 has A629 buses that can be dual, triple (flight controls) or quadruple (engine controllers) for redundancy. A triple bus means the information is send on 3 buses in parallel, using 3 bus interfaces, like this:


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The primary flight controllers have three lanes allocated to different functions: command, monitor and standby. Each lane is connected to a different bus of the triplex. 

A629 is in many points similar to thin Ethernet (e.g. 10Base2) but uses a twisted pair instead of coaxial cable for the physical layer:


Bi-directional: Contrary to A429, A629 is bi-directional, data can travel in any direction,
From any interface to any other interface,
The bus is a twisted cable, 
Terminators are fitted at both sides to prevent signal reflection and stationary waves,
A stub connects the unit to the bus using a coupler,
Couplers are plugged directly on the cable without cutting the wires.



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Coupler: This is actually a transformer and data are transmitted by induction.


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Data: Data on the bus are digital, coded with Manchester bi-phase.

AFDX

AFDX (Avionics Full-Duplex Switched Ethernet) is similar to 802.3 Switched Ethernet Standard. The physical layer can be a shielded twisted pair or an optical fiber.

Instead of a bus topology it uses a star topology. Switches are used to connect the different nodes.


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The particularities of the switched network:


Data don't flow to each units on the same bus, the network can be segmented to reduce contention (collisions).
Since the broadcast domain is reduced, this allows for higher data rates.
Deterministic transfer times can be achieved, something which is important in real time applications.


AFDX also allows for virtual links, that is defining a point to point virtual circuit, to completely abstract the network layer.