In copper cabling such as twisted pair Ethernet, what is the specific term for unwanted signal interference that is induced from adjacent wire pairs within the same cable?

Introduction / Context:
When transmitting data over copper cables, several types of interference and signal degradation can occur. Understanding the terminology helps in diagnosing cable problems and choosing appropriate cabling for a given environment. The question focuses on interference between adjacent pairs within the same cable, which is a common concern for twisted pair Ethernet cabling.

Given Data / Assumptions:

We are dealing with twisted pair copper cabling, such as Category 5 or Category 6 Ethernet cables.
Interference originates from signals on neighboring wire pairs inside the same physical cable, not from outside sources.
We need to identify the technical term for this kind of interference.

Concept / Approach:
Crosstalk is the term used to describe unwanted coupling of signals from one pair of wires to another pair within the same cable. It occurs because electromagnetic fields generated by a signal on one pair induce currents on adjacent pairs. EMI and RFI generally refer to interference from external sources, while attenuation refers to signal loss over distance and reflection relates to impedance mismatches.

Step-by-Step Solution:
Identify that the interference originates from adjacent wire pairs within the same cable jacket. Recognize that this pattern of interference is called crosstalk, specifically near end crosstalk (NEXT) or far end crosstalk (FEXT) depending on where it is measured. EMI and RFI refer to external sources like motors, fluorescent lights or radio transmitters, which is not the scenario described here. Attenuation is a gradual loss of signal strength as it travels along the cable, not interference from another pair. Thus, the correct term for interference from adjacent pairs is crosstalk.

Verification / Alternative check:
Cable certification tools measure and report crosstalk values, often labeling them as NEXT or FEXT in their reports. Standards for twisted pair cabling specify maximum allowable crosstalk levels at various frequencies. This confirms that the industry uses the term crosstalk for internal pair to pair interference.

Why Other Options Are Wrong:
Option a (EMI) refers broadly to interference from external electromagnetic sources, not specifically from neighboring pairs inside the same cable.
Option b (RFI) is a subset of EMI related to radio frequencies from external sources, not internal cable pair coupling.
Option d (attenuation) is signal loss over distance and does not describe interference from other signals.
Option e (reflection) occurs when a signal encounters an impedance mismatch and part of it is reflected back; it is not the same as pair to pair interference.

Common Pitfalls:
A common mistake is to use EMI as a catch all term for any interference, but exam questions frequently require the more precise term crosstalk for within cable interference. Proper cable installation practices, such as maintaining twists up to the termination and avoiding kinks, help reduce crosstalk and maintain signal quality.

Final Answer:
The unwanted interference from adjacent pairs in the cable is called crosstalk.