Optical waveguides – Optical fiber waveguide with cladding – Utilizing multiple core or cladding
Reexamination Certificate
2002-08-26
2004-11-16
Bruce, David V. (Department: 2882)
Optical waveguides
Optical fiber waveguide with cladding
Utilizing multiple core or cladding
Reexamination Certificate
active
06819850
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to optical fiber transmission systems, more specifically to wavelength division multiplex transmission systems.
2. Description of the Prior Art
The index profile of optical fibers is generally characterized as a function of the shape of the graph of the function which associates the refractive index and the radius of the fiber. It is conventional to plot the distance r from the center of the fiber on the abscissa axis and the difference between the refractive index and the refractive index of the cladding of the fiber on the ordinate axis. The expressions “step”, “trapezium” and “triangle” are used for the index profiles of graphs which are respectively step-shaped, trapezium-shaped and triangular. These curves are generally representative of the theoretical or set point profile of the fiber and fiber fabrication constraints can yield a significantly different profile.
It is advantageous to control chromatic dispersion in new wavelength division multiplex transmission networks using high bit rates, especially bit rates greater than or equal to 40 Gbit/s or 160 Gbit/s; the objective is to obtain substantially zero cumulative chromatic dispersion over the link for all wavelengths of the multiplex, in order to limit widening of the pulses. A cumulative dispersion value of several tens of ps
m is generally acceptable. It is also useful to avoid zero values of local chromatic dispersion, at which nonlinear effects are more accentuated, in the vicinity of wavelengths used in the system. Finally, it is also useful to limit the chromatic dispersion slope over the range of the multiplex; low slope values limit distortion between channels of the multiplex and facilitate compensation of chromatic dispersion over the whole of the multiplex. The chromatic dispersion slope is conventionally the derivative of the chromatic dispersion with respect to wavelength.
Stepped-index fiber, also known as single-mode fiber (SMF), is conventionally used as line fiber in optical fiber transmission systems. The prior art ASMF 200 single-mode fiber has a chromatic dispersion of the order of 17 ps/(nm.km) at 1 550 nm. The chromatic dispersion slope at 1 550 nm is of the order of 0.06 ps/(nm
2
.km).
Dispersion-shifted fibers (DSF) are now available off the shelf. Non-zero dispersion-shifted fibers (NZ-DSF+) are dispersion-shifted fibers with a positive non-zero chromatic dispersion at the wavelengths at which typically around 1 550 nm. At these wavelengths these fibers have a low chromatic dispersion, typically less than 11 ps/(nm.km) at 1 550 nm, and a chromatic dispersion slope from 0.04 ps/(nm
2
.km) to 0.1 ps/(nm
2
.km).
FR-A2 790 107 proposes a line fiber which is particularly suitable for dense wavelength division multiplex transmission with a channel spacing of 100 GHz or less for a bit rate per channel of 10 Gbit/s or more; at a wavelength of 1 550 nm, this fiber has an effective surface area greater than or equal to 60 &mgr;m
2
, a chromatic dispersion from 6 ps/(nm.km) to 10 ps/(nm.km), and a chromatic dispersion slope less than 0.07 ps/(nm
2
.km). At this wavelength, the bending losses with the fiber wound around a 10 mm radius former are of the order of 10 dB/m. At a wavelength of 1 625 nm, the bending losses reach 50 dB/m.
French patent application No. 0002316 filed Feb. 24, 2000 (published Aug. 31, 2001, publication number 2 805 620), whose title in translation is “An optical fiber providing monomode propagation when incorporated into a cable, for wavelength division multiplex optical fiber transmission networks”, proposes a line fiber having at 1 550 nm a chromatic dispersion from 5 ps/(nm.km) to 11 ps/(nm.km), a chromatic dispersion slope from 0.014 ps/(nm
2
.km) to 0.044 ps/(nm
2
.km) and bending losses measured by winding the fiber around a 10 mm radius former of the order of 10 dB/m. At a wavelength of 1 625 nm the bending losses reach 50 dB/m.
The invention proposes a fiber which has a low (virtually zero) chromatic dispersion slope compared to these non-zero dispersion-shifted fibers and thus an almost constant chromatic dispersion over a wider range of wavelengths, which limits distortion between channels. The fiber can therefore be used in a wavelength division multiplex transmission system with a larger number of channels.
SUMMARY OF THE INVENTION
To be more precise, the invention proposes an optical fiber in which propagation is monomode propagation at a range of wavelengths from 1 300 nm to 1 700 nm when incorporated into a cable, said fiber having:
at a wavelength of 1 550 nm, a chromatic dispersion C from 3 ps/(nm.km) to 14 ps/(nm.km) and an absolute value of chromatic dispersion slope C′ less than 0.014 ps/(nm
2
.km), and
at a wavelength of 1 625 nm, bending losses measured for a 10 mm radius less than 400 dB/m.
The fiber can advantageously have one or more of the following optical characteristics:
at a wavelength of 1 550 nm an effective surface area greater than or equal to 35 &mgr;m
2
, preferably greater than or equal to 40 &mgr;m
2
;
a chromatic dispersion cancellation wavelength &lgr;
0
less than or equal to 1 400 nm;
at a wavelength of 1 550 nm a mode diameter 2W
02
greater than or equal to 6.4 &mgr;m;
at a wavelength of 1 550 nm bending losses measured for a 10 mm radius less than 100 dB/m;
at a wavelength of 1 625 nm, and preferably at a wavelength of 1 675 nm, bending losses of less than 400 dB/m measured for a 10 mm radius;
at a wavelength of 1 550 nm bending losses of less than 10
−2
dB measured for 100 turns of fiber around a 30 mm radius former;
at a wavelength of 1 625 nm bending losses of less than 0.1 dB measured for 100 turns of fiber around a 30 mm radius former;
at a wavelength of 1 675 nm bending losses of less than 0.5 dB measured for 100 turns of fiber around a 30 mm radius former;
a theoretical cut-off wavelength less than or equal to 1 850 nm and preferably less than or equal to 1 800 nm;
an absolute value of the variation of chromatic dispersion at wavelengths from 1 460 nm to 1 625 nm, relative to its value at 1 550 nm, less than or equal to 35%, and preferably less than or equal to 25%, or even less than or equal to 20%;
an absolute value of the variation of chromatic dispersion at wavelengths from 1 460 nm to 1 675 nm, relative to its value at 1 550 nm, less than or equal to 40%, and preferably less than or equal to 35%, or even less than or equal to 25%;
an absolute value of the variation of chromatic dispersion at wavelengths from 1 460 nm to 1 625 nm, relative to its value at 1 550 nm, less than or equal to 2 ps/(nm.km), and preferably less than or equal to 1 ps/(nm.km);
an absolute value of the variation of chromatic dispersion at wavelengths from 1 460 nm to 1 675 nm, relative to its value at 1 550 nm, less than or equal to 3 ps/(nm.km), and preferably less than or equal to 2 ps/(nm.km);
at a wavelength of 1 550 nm a chromatic dispersion C from 5 ps/(nm.km) to 11 ps/(nm.km);
at a wavelength of 1 550 nm an absolute value of the chromatic dispersion slope C′ less than or equal to 0.012 ps/(nm
2
.km) and preferably less than 0.010 ps/(nm
2
.km);
an absolute value at a wavelength of 1 550 nm of the product of the effective surface area and the ratio between chromatic dispersion and chromatic dispersion slope greater than 12 000 &mgr;m
2
.nm;
at a wavelength of 1 550 nm a sensitivity to microbending less than or equal to 1 and preferably less than or equal to 0.8;
at a wavelength of 1 550 nm an attenuation less than or equal to 0.24 dB/km;
at a wavelength of 1 550 nm a polarization mode dispersion less than or equal to 0.2 ps/km
1/2
, and preferably less than or equal to 0.1 ps/km
1/2
, or even less than or equal to 0.05 ps/km
1/2
.
The index profile of one embodiment of the fiber is a trapezium or rectangle with a buried trench and a ring. In this case, the characteristics of the profile can advantageously be chosen from the following characteristics:
the difference (&Dgr;n
1
) between the index of the trapezium or the rectangle and the in
Beaumont Florent
de Montmorillon Louis-Anne
Fleury Ludovic
Gorlier Maxime
Nouchi Pascale
Alcatel
Artman Thomas
Bruce David V.
Suhgrue Mion, PLLC
LandOfFree
Optical fiber for a wavelength division multiplex... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical fiber for a wavelength division multiplex..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical fiber for a wavelength division multiplex... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3328368