Bending Loss vs Radius

In-plane bend, Marcuse-style radiation loss. EIM modal parameters from W (bend direction) slab.

Wavelength (μm) WG width W (μm) WG height H (μm) Δ (%) Bend angle θ (deg) R (readout) (mm) Plot R_min (mm) Plot R_max (mm)

n_core (Sellmeier)

—

n_clad

—

n_eff (total)

—

γ_x (cladding decay)

—

β (propagation)

—

α at R (per mm)

—

Loss @ R, θ

—

Quality at this R

—

R critical for 0.1 dB

—

R critical for 1.0 dB

—

Loss vs bend radius (log-log). X-range set by R_min/R_max inputs. Green / orange dashed lines mark 0.1 dB and 1 dB thresholds. Black dashed vertical line is your selected R.

Equations

α(R) = (γ/2)·exp(−2γ·a)·exp(−B·R), B = 2γ³ / (3β²), a = W/2

Loss(dB) = 4.343 · α(R) · R · θ (arc length L = R·θ)

Loss has a peak at R = 1/B; the design-relevant root is on the right (large-R) side.

Reference implementations

bending_loss.py BendingLossCalculator.java