Silicon photonics
For relatively short-reach optical links inside data centers, which is a correct reason wavelengths around 1.31 µm (O-band) are often used?
- AFiber loss is the lowest of all wavelengths, so signals reach thousands of km without amplifiers
- BChromatic dispersion in standard single-mode fiber is nearly zero, so high-speed signal waveforms are less distorted
- CThe photon energy equals silicon's band gap, so silicon can be used as-is for the photodetector
Show answer and explanation
Answer: B. Chromatic dispersion in standard single-mode fiber is nearly zero, so high-speed signal waveforms are less distorted
Chromatic dispersion is the spreading of optical pulses caused by slight differences in propagation speed through the fiber at different wavelengths. In standard single-mode fiber, dispersion is nearly zero around 1.31 µm, so high-speed signals can easily be sent a few km to about 10 km without dispersion compensation, and many data center optical transceivers use this band. Loss is lowest around 1.55 µm (about 0.2 dB/km); at 1.31 µm it is somewhat higher, about 0.3–0.35 dB/km. The photon energy at 1.31 µm is about 0.95 eV, which silicon does not absorb.