Which wavelength characteristic eliminates physical port dependency for colorless add/drop?

Question

Options

• Abit rate
• Bdirection
• Cprotocol
• Dfrequency

• A
  4% (1)
• B
  4% (1)
• C
  13% (3)
• D
  78% (18)

Explanation

Frequency (the "color" of light) is what defines a specific wavelength channel in optical networking - a "colorless" add/drop port is one that is not locked to a particular frequency, so any port can handle any wavelength without requiring a dedicated physical mapping. This frequency-agnosticism is exactly what eliminates port dependency: since no port is pre-assigned to a specific color, signals can be added or dropped anywhere.

Why the others are wrong:

• A (bit rate): Bit rate describes data speed, not channel identity. Rate-agnostic features exist but address a different problem ("rate-transparent"), unrelated to port-to-wavelength binding.
• B (direction): Direction refers to "directionless" capability - a separate ROADM feature meaning a port isn't locked to a specific fiber degree or cardinal direction. Easy to confuse, but it's a distinct dimension.
• C (protocol): Protocol independence concerns data format (Ethernet, OTN, etc.), not how wavelengths are assigned to physical ports.

Memory tip: Think of it literally - "colorless" = no fixed color = no fixed frequency. In optics, color is frequency, so a colorless port is a frequency-flexible port. If you remember that light's color comes from its frequency, "colorless = frequency-independent" locks in immediately.

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