# US 5,329,607 A · Pure-silica core dual-mode optical fiber

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- Number: US 5,329,607 A
- Document ID: US5329607A
- Status: Granted
- Kind: A
- Application number: 07/988,607
- Filed: 1992-02-28
- Granted: 1994-07-12
- Earliest claimed: 1992-02-28
- Assignees: The United States of America as represented by the Secretary of the Navy
- Inventors: Neil T. Kamikawa; Arthur T. Nakagawa
- Web page: https://patentgrep.com/patent/US5329607A

## CPC

- G02B 6/02047: {Dual mode fibre (G02B6/105 takes precedence)}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An improved dual-mode optical fiber provides for an improved combination of spectral attenuation, bending losses and modal noise and modal dispersion for long-haul transmission at 1550 nm. The dual-mode optical fiber has a pure-silica core and a silica cladding depressed with fluorine so that the core and cladding have a relative refractive index difference, .DELTA., of about 0.72% and a second-mode cutoff wavelength, .lambda..sub.c, at 1630 nm. Optionally, a non-silica core and cladding can be used for long-haul transmission at 1550 nm. when the core and cladding have a relative refractive index difference, .DELTA., of about 0.72% and a second-mode cutoff wavelength, .lambda..sub.c, at 1630 nm.

## Claims

### Claim 1

An improved dual-mode optical fiber in which dual-mode propagation having a cutoff wavelength greater than an operating wavelength of both the fundamental LP.sub.01 and second-order LP.sub.11 modes to provide an improved combination of spectral attenuation, bending losses and modal noise and modal dispersion for long-haul transmission at said operating wavelength of about 1550 nm comprising:
a pure-silica core to provide for reduced Rayleigh scattering and
a silica cladding depressed with fluorine, said core and cladding having a relative refractive index difference, .DELTA., of about 0.72% and a second-mode cutoff wavelength, .lambda..sub.c, at about 1630 nm to thereby provide said dual-mode propagation with said cutoff wavelength being greater than said operating wavelength of both the fundamental LP.sub.01 and second-order LP.sub.11 modes.

### Claim 2

An improved dual-mode optical fiber in which dual-mode propagation having a cutoff wavelength greater than an operating wavelength of both the fundamental LP.sub.01 and second-order LP.sub.11 modes to provide an improved combination of spectral attenuation, bending losses and modal noise and modal dispersion for long-haul transmission at about 1550 nm comprising:
a non-silica core and
a cladding, said core and cladding having a relative refractive index difference, .DELTA., of about 0.72% and a second-mode cutoff wavelength, .lambda..sub.c, at about 1630 nm to thereby provide said dual-mode propagation with said cutoff wavelength being greater than an operating wavelength of both the fundamental LP.sub.01 and second-order LP.sub.11 modes.