The fraction of optical power lost to scattering and absorption as light travels through a waveguide or fiber, expressed in dB/cm or dB/km. In silicon waveguides the main cause is scattering from sidewall roughness, with typical values around 1 to 3 dB/cm, far higher than fiber's roughly 0.2 dB/km.
Japanese name: 伝搬損失
Propagation loss appears in 4 practice questions across 1 topic, including Silicon photonics.
Field: Silicon photonics
Answer: A. About 79%
5 mm is 0.5 cm, so the loss is 2 dB/cm × 0.5 cm = 1 dB. The loss L in dB and the transmittance T are related by T = 10^(−L/10); 10^(−0.1) ≈ 0.79, so about 79% remains. It is handy to remember that 3 dB is roughly half and 10 dB is one-tenth. About 90% corresponds to a loss of 0.5 dB, and about 50% to a loss of 3 dB. Using dB turns the multiplication of each component's transmittance into addition, making it easy to total the losses of multiple components.
Answer: A. Light scattering from fine roughness on sidewalls created by etching
In silicon waveguides, roughness of a few nm formed on the sidewalls by lithography and etching scatters light out of the waveguide. Because the index contrast between silicon and oxide is large and the waveguide is thin, the light intensity at the sidewalls is also high, so scattering has a strong effect. Propagation loss of a typical strip waveguide is roughly 1–3 dB/cm depending on conditions (below 1 dB/cm in low-loss processes), and it is reduced by using rib waveguides, widening the waveguide, or smoothing the sidewalls by oxidation or annealing in hydrogen. The photon energy at telecom wavelengths is smaller than silicon's band gap, so band-to-band absorption does not occur.
Propagation loss of a typical strip waveguide is roughly 1–3 dB/cm depending on conditions (below 1 dB/cm in low-loss processes), and it is reduced by using rib waveguides, widening the waveguide, or smoothing the sidewalls by oxidation or annealing in hydrogen.
Which is considered one of the main causes of propagation l…Loss also arises from fiber coupling at the waveguide's input and output, so measuring the transmission of a single waveguide cannot separate propagation loss from coupling loss.
Which correctly describes the cutback method for measuring …On the other hand, the larger the index contrast, the more sidewall roughness scatters light, so propagation loss—though condition-dependent—is about 1–3 dB/cm for a typical strip waveguide (lower for rib waveguides or low-loss processes), far greater than fiber's (about 0.2 dB/km).
Which correctly describes a silicon waveguide (refractive i…As an Amazon Associate I earn from qualifying purchases.
Waveguide Annealing Band gap Refractive index C-band Chromatic dispersion CPO (co-packaged optics) Edge coupler Extinction ratio Grating coupler