• It is common to wrap optical fiber in communication systems

OPTI 500 C, Spring 2011, Lecture 24, Bend Loss, Nonlinear Effects 1

Bend Loss in Optical Fibers

• Power in the tail of the mode profile is lost.

OPTI 500 C, Spring 2011, Lecture 24, Bend Loss, Nonlinear Effects 2

Bend Loss in Optical Fibers

From Integrated Optics, Robert G. Hunsperger, 4th Edition, pp. 84-87.

• Keeping bend radii greater than 10 cm makes bend loss negligible

OPTI 500 C, Spring 2011, Lecture 24, Bend Loss, Nonlinear Effects 3

Bend Loss in Optical Fibers

From Photonics, Yariv and Yeh, 4th Edition

OPTI 500 C, Spring 2011, Lecture 24, Bend Loss, Nonlinear Effects 4

OPTI 500 C, Spring 2011, Lecture 24, Bend Loss, Nonlinear Effects 5

OPTI 500 C, Spring 2011, Lecture 24, Bend Loss, Nonlinear Effects 6

OPTI 500 C, Spring 2011, Lecture 24, Bend Loss, Nonlinear Effects 7

OPTI 500 C, Spring 2011, Lecture 24, Bend Loss, Nonlinear Effects 8

Draka BendBright-Elite Fiber (G.657.B3)

• Larger core-clad index difference minimizes bend loss, but smaller mode profiles increase splice loss

• Fiber with a trench-index profile minimizes bend loss while maintaining a larger mode profile

OPTI 500 C, Spring 2011, Lecture 24, Bend Loss, Nonlinear Effects 9

Low Bend Loss Optical Fiber

From “Low-Bending-Loss Single-Mode Fibers for Fiber-to-the-Home,” Himeno, Matsuo, and Guan, J. Lightwave Tech. Vol. 23, (11) 2005, p. 3494

• Self-Phase Modulation • Four-Wave Mixing

OPTI 500 C, Spring 2011, Lecture 24, Bend Loss, Nonlinear Effects 10

Nonlinear Impairments in Optical Fiber

• An increasing intensity, and refractive index, has the effect of increasing frequency (decreasing wavelength) and vice versa

OPTI 500 C, Spring 2011, Lecture 24, Bend Loss, Nonlinear Effects 11

Nonlinear Impairments in Optical Fiber

( ) ( )( )

( )

0 2

2 20

0

2 22 02

0

exp /

2 2 exp /

n n n I

I t I t

ttn L I t

τ

ω ω ω

π τλ τ

= +

= −

∆ = −

= −

From Photonics, Yariv and Yeh, 4th Edition

OPTI 500 C, Spring 2011, Lecture 24, Bend Loss, Nonlinear Effects 12

Four-Wave Mixing

Simulations from “Four-Photon Mixing And High-Speed WDM Systems, Tkach et al. J. Lightwave Tech. Vol. 13 (5) 1995, p. 841

Eye Diagram - Output

Eye Diagram - Input WDM Input

WDM Output