Optical transmission systems and methods using a QSM large-effective-area optical fiber

Patent metadata

Field	Value
Publication number	US-9841555-B2
Application number	US-201514862681-A
Country	US
Kind code	B2
Filing date	Sep 23, 2015
Priority date	Sep 29, 2014
Publication date	Dec 12, 2017
Grant date	Dec 12, 2017

Abstract

Optical transmission systems and methods are disclosed that utilize a QSM optical fiber with a large effective area and that supports only two modes, namely the fundamental mode and one higher-order mode. The optical transmission system includes a transmitter and a receiver optically coupled by an optical fiber link that includes at least one section of the QSM optical fiber. Transmission over optical fiber link gives rise to MPI, which is mitigated using a digital signal processor. The QSM optical fiber is designed to have an amount of DMA that allows for the digital signal processor to have reduced complexity as reflected by a reduced number of filter taps as compared to if the DMA were zero.

First claim

What is claimed is:

1. An optical transmission system, comprising:
a quasi-single mode (QSM) optical fiber configured to support a fundamental mode having effective area A eff >170 μm 2 for a wavelength of 1550 nm and an attenuation of no greater than 0.2 dB/km for a wavelength of 1530 nm, and to support a single higher-order mode having a differential modal attenuation (DMA) of at least 1.0 dB/km at a wavelength of 1530 nm;
an optical transmitter optically coupled to the QSM optical fiber and configured to emit light that defines an optical signal that carries information;
an optical receiver optically coupled to the optical transmitter by the QSM optical fiber and configured to receive the light emitted by the optical transmitter and transmitted over the QSM optical fiber in the fundamental mode and the single higher-order mode, wherein the transmission of the optical signals over the QSM optical fiber gives rise to multipath interference (MPI), and wherein the optical receiver generates an analog electrical signal representative of the received light;
an analog-to-digital converter (ADC) electrically connected to the optical receiver and that converts the analog electrical signal into a corresponding digital electrical signal; and
a digital signal processor electrically connected to the ADC and configured to receive and process the digital electrical signal to mitigate the MPI and generate a processed digital signal representative of the optical signal from the optical transmitter, wherein the digital signal processor includes a number N T of filter taps, and wherein the number N T of filter taps is reduced by at least 60% as compared to if the DMA of the QSM optical fiber were equal to zero.

2. The method according to claim 1 , wherein the DMA is at least 2.0 dB/km, and wherein the number N T of filter taps is reduced by at least 80%.

3. The method according to claim 1 , wherein the DMA is at least 3.0 dB/km, and wherein the number N T of filter taps is reduced by at least 87%.

4. The method according to claim 1 , wherein the DMA is at least 4.0 dB/km, and wherein the number N T of filter taps is reduced by at least 90%.

5. The optical transmission system according to claim 1 , wherein the QSM optical fiber has a core with a radius that is greater than 5 μm.

6. The optical transmission system according to claim 1 , wherein the QSM optical fiber has a core with a radius that is greater than 7 μm.

7. The optical transmission system according to claim 1 , wherein the QSM optical fiber has a cutoff wavelength λc>1600 nm.

8. The optical transmission system according to claim 1 , wherein the QSM optical fiber includes a core and a cladding surrounding the core, wherein the cladding includes an inner annular cladding region of refractive index n 2 immediately adjacent the core, and a moat of refractive index n 3 immediately adjacent the inner annular cladding region, and wherein n 2 >n 3 .

9. The optical transmission system according to claim 1 , wherein the effective area A eff >200 μm 2 and wherein the QSM optical fiber has a bending loss of BL<0.02 dB/turn for a wavelength of 1625 nm and for a bend diameter D B =60 mm.

10. The optical transmission system according to claim 1 , wherein attenuation of the fundamental mode is no greater than 0.17 dB/km, and wherein for the fundamental mode LP 01 the bending loss BL<0.005 dB/turn at 1625 nm for the bend diameter D B =60 mm.

11. An optical transmission system, comprising:
an optical fiber link having at least one section of quasi-single mode (QSM) optical fiber having: a core having a centerline and an outer edge, with a peak refractive index n 0 on the centerline and a refractive index n 1 at the outer edge; a cladding section surrounding the core, wherein the cladding section includes a first inner annular cladding region immediately adjacent the core; wherein the core and cladding section support a fundamental mode LP 01 and a higher-order mode LP 11 and define: i) for the fundamental mode LP 01 : an effective area A eff >170 μm 2 for a wavelength of 1550 nm and an attenuation of no greater than 0.2 dB/km for a wavelength of 1530 nm; ii) for the higher-order mode LP 11 : a differential modal attenuation (DMA) of at least 1.0 dB/km for the wavelength of 1530 nm; and iii) a bending loss of BL<0.02 dB/turn for a wavelength of 1625 nm and for a bend diameter D B =60 mm;
an optical transmitter configured to emit light that defines an optical signal that carries information;
an optical receiver optically coupled to the optical transmitter by the at least one section of QSM optical fiber and configured to receive the light emitted by the optical transmitter and transmitted over the QSM optical fiber in the fundamental mode LP 01 and the higher-order mode LP 11 thereby giving rise to multipath interference (MPI), wherein the optical receiver generates an analog electrical signal from the received light;
an analog-to-digital converter (ADC) electrically connected to the optical receiver and that converts the analog electrical signal into a corresponding digital electrical signal; and
a digital signal processor electrically connected to the ADC and configured to receive and process the digital electrical signal to mitigate the MPI and generate a processed digital signal representative of the optical signal from the optical transmitter, wherein the digital signal processor includes a number N T of filter taps, and wherein the number N T of filter taps is reduced by at least 60% as compared to if the DMA of the QSM optical fiber were equal to zero.

12. The method according to claim 11 , wherein the DMA is at least 2.0 dB/km, and wherein the number N T of filter taps is reduced by at least 80%.

13. The method according to claim 11 , wherein the DMA is at least 3.0 dB/km, and wherein the number N T of filter taps is reduced by at least 87%.

14. The method according to claim 11 , wherein the DMA is at least 4.0 dB/km, and wherein the number N T of filter taps is reduced by at least 90%.

15. The method according to claim 11 , wherein the effective area A eff >200 μm 2 .

16. An optical transmission method, comprising:
transmitting optical signals over an optical fiber link having at least one section of quasi-single mode (QSM) optical fiber configured to support a fundamental mode having an effective area A eff >170 μm 2 for a wavelength of 1550 nm and an attenuation of no greater than 0.2 dB/km for a wavelength of 1530 nm, and to support a single higher-order mode having a differential modal attenuation (DMA) of at least 1.0 dB/km at a wavelength of 1530 nm, wherein the transmitting of the optical signals gives rise to multipath interference (MPI);
receiving the transmitted optical signals with an optical receiver and generating in response analog electrical signals representative of the optical signals and including the MPI;
converting the analog electrical signals to digital electrical signals; and
processing the digital electrical signals with a digital signal processor that includes a number N T of filter taps configured to mitigate the MPI, wherein the number N T of filter taps is reduced by at least 60% as compared to if the DMA were zero.

17. The method according to claim 16 , wherein the DMA is at least 2.0 dB/km, and wherein the number N T of filter taps is reduced by at least 80%.

18. The method according to claim 16 , wherein the DMA is at least 3.0 dB/km, and wherein the number N T of filter taps is reduced by at least 87%.

19. The method according to claim 16 , wh

Assignees

• Corning Inc

Inventors

• Downie John David
• Li Ming-Jun
• Mlejnek Michal
• ROUDAS Ioannis Georgios
• Wood William Allen
• Zakharian Aramais Robert

Classifications

• G02B6/03611

  Highest index adjacent to central axis region, e.g. annular core, coaxial ring, centreline depression affecting waveguiding · CPC title

• H04B10/2504

  Electricity · mapped topic

• G02B6/0286

  Combination of graded index in the central core segment and a graded index layer external to the central core segment (G02B6/0288 takes precedence) · CPC title

• G02B6/28

  having data bus means, i.e. plural waveguides interconnected and providing an inherently bidirectional system by mixing and splitting signals · CPC title

• G02B6/02047

  Dual mode fibre (G02B6/105 takes precedence) · CPC title