Fiber connectors for mode division multiplexing using multimode optical fibers

Abstract

A first multimode optical fiber carries a mode division multiplexed (MDM) optical signal. The MDM optical signal is transmitted into a second multimode fiber from the first multimode optical fiber. The first and second multimode fibers are coupled via a fiber connector. The lateral offset between the two fibers at the connector is less than 2 μm.

What we claim as the invention is: 
     
         1 . An optical system, comprising
 a transmitter portion comprising at least a first optical transmitter capable of generating a first optical signal;   a first multimode optical fiber having a first end and a second end, the first multimode optical fiber having a gradient index core;   a first mode division multiplexing (MDM) optical arrangement between the first optical transmitter and the first end of the first multimode optical fiber to selectively direct the first optical signal into a fundamental linear polarization (LP) mode, an LP 01  mode, of the first multimode optical fiber;   a second multimode optical fiber having a first end and a second end, the second multimode optical fiber having a gradient index core;   a multimode fiber connector attached to the second end of the first multimode optical fiber and the first end of the second multimode optical fiber to transmit the first optical signal from the first multimode optical fiber into an LP 01  mode of the second multimode optical fiber;   a receiver portion comprising at least a first optical receiver; and   a second MDM optical arrangement disposed between the second end of the second multimode optical fiber and the first optical receiver to selectively direct the first optical signal that has propagated along the LP 01  mode of the second multimode optical fiber to the first optical receiver.   
     
     
         2 . The system as recited in  claim 1 ,
 wherein the transmitter portion further comprises a second optical transmitter capable of generating a second optical signal, and the receiver portion further comprises a second optical receiver,   wherein first MDM optical arrangement selectively directs the second optical signal into a first mode group of the first multimode optical fiber, the first mode group comprising one of i) LP 11a  and LP 11b  modes of the first multimode optical fiber, ii) LP 02 , LP 21a  and LP 21b  modes of the first multimode optical fiber or iii) LP 31a , LP 31b , LP 12a  and LP 12b  modes of the first multimode optical fiber,   wherein the multimode fiber connector aligns the second end of the first multimode optical fiber with the first end of the second multimode optical fiber so that the second optical signal is transmitted into a first mode group of the second multimode fiber comprising the same LP modes of the second multimode fiber as the first mode group of the first multimode optical fiber, and   wherein the second MDM optical arrangement selectively directs the second optical signal to the second optical receiver.   
     
     
         3 . The system as recited in  claim 1 , wherein the multimode fiber connector comprises a first housing containing a first ferrule at the second end of the first multimode optical fiber and a second housing containing a second ferrule at the first end of the second fiber. 
     
     
         4 . The system as recited in  claim 1 , wherein the multimode fiber connector comprises a ferrule-less multimode fiber connector having a first pressure element at the second end of the first multimode optical fiber and a second pressure member at the first end of the second multimode optical fiber. 
     
     
         5 . The system as recited in  claim 1 , wherein a lateral offset between the second end of the first multimode optical fiber and the first end of the second multimode optical fiber is less than 2 μm. 
     
     
         6 . An optical system, comprising
 a first optical fiber, the first optical fiber being a graded index multimode fiber having a first end and a second end;   a second optical fiber, the second optical fiber being a graded index multimode fiber having a first end and a second end;   a multimode fiber connector coupling the second end of the first optical fiber to the first end of the second optical fiber;   a transmitter portion arranged to direct a mode division multiplexed (MDM) optical signal into the first end of the first fiber, the MDM optical signal comprising at least a first optical signal propagating along a first mode group of the first optical fiber and a first mode group of the second optical fiber, and a second optical signal propagating along a second mode group of the first optical fiber and a second mode group of the second optical fiber;   a receiver portion arranged to separately detect the first optical signal and the second optical signal after propagating through the second optical fiber.   
     
     
         7 . The system recited in  claim 6 , wherein the transmitter portion comprises a first transmitter unit to generate the first optical signal, a second transmitter unit to generate the second optical signal and a mode division multiplexer to direct the first optical signal into the first mode group of the first optical fiber and the second optical signal into a second mode group of the first optical fiber. 
     
     
         8 . The system recited in  claim 7 , wherein the receiver portion comprises a first optical receiver, a second optical receiver and a mode division demultiplexer to direct the first optical signal from the second optical fiber to the first optical receiver and the second optical signal from the second optical fiber to the second optical receiver. 
     
     
         9 . The system recited in  claim 6 , wherein the first mode group of the first multimode optical fiber is a fundamental linear polarization (LP) mode, an LP 01  mode, and the first mode group of the second multimode optical fiber is an LP 01  mode of the second multimode optical fiber. 
     
     
         10 . The system recited in  claim 9 , wherein the second mode group of the first multimode optical fiber comprises LP 11a  and LP 11b  modes of the first multimode optical fiber, and the second mode group of the second multimode optical fiber comprises LP 11a  and LP 11b  modes of the second multimode optical fiber. 
     
     
         11 . The system recited in  claim 9 , wherein the second mode group of the first multimode optical fiber comprises LP 02 , LP 21a  and LP 21b  modes of the first multimode optical fiber, and the second mode group of the second multimode optical fiber comprises LP 02 , LP 21a  and LP 21b  modes of the second multimode optical fiber. 
     
     
         12 . The system recited in  claim 9 , wherein the second mode group of the first multimode optical fiber comprises LP 31a , LP 31b , LP 12a  and LP 12b  modes of the first multimode optical fiber, and the second mode group of the second multimode optical fiber comprises LP 31a , LP 31b , LP 12a  and LP 12b  modes of the second multimode optical fiber. 
     
     
         13 . The system recited in  claim 6 , wherein a lateral offset between the first and second multimode optical fibers in the multimode fiber connector is less than 2 μm. 
     
     
         14 . The system recited in  claim 6 , wherein the first optical receiver receives the second optical signal at a signal level at least 7 dB less than the first optical signal and the second optical receiver receives the first optical signal at a signal level at least 7 dB less than the second optical signal. 
     
     
         15 . The system as recited in  claim 6 , wherein the first and second optical fibers each have a nominal core diameter of 50 μm. 
     
     
         16 . The system as recited in  claim 6 , wherein the first optical signal is a wavelength division multiplexed optical signal. 
     
     
         17 . A method, comprising:
 generating a first optical signal at a first optical transmitter;   selectively directing the first optical signal into a first mode group of a first multimode optical fiber having a gradient index core, the first mode group of the first multimode optical fiber being a fundamental linear polarization (LP) mode, LP 01 , of the first multimode optical fiber, the first multimode optical fiber being connected to a second multimode optical fiber by a multimode fiber connector, the second multimode optical fiber having a gradient index core;   transmitting the first optical signal from the first multimode optical fiber into a first mode group of the second multimode optical fiber, the first mode group of the second multimode optical fiber being a LP 01  mode of the second multimode optical fiber;   selecting the first optical signal after propagating along the LP 01  mode of the second multimode optical fiber; and   detecting the selected first optical signal at a first optical receiver.   
     
     
         18 . A method as recited in  claim 17 , further comprising
 generating a second optical signal at a second optical transmitter;   selectively directing the second optical signal into a second mode group of the first multimode optical fiber,   transmitting the second optical signal from the first multimode optical fiber into a second mode group of the second multimode optical fiber;   selecting the second optical signal after propagating along the second mode group of the second multimode optical fiber; and   detecting the selected second optical signal at a second optical receiver.   
     
     
         19 . A method as recited in  claim 18 , wherein the second mode group of the first multimode optical fiber comprises one of i) LP 11a  and LP 11b  modes of the first multimode optical fiber, ii) LP 02 , LP 21a  and LP 21b  modes of the first multimode optical fiber or iii) LP 31a , LP 31b , LP 12a  and LP 12b  modes of the first multimode optical fiber, and wherein the second mode group of the second multimode optical fiber comprises the same LP modes as the second mode group of the first multimode optical fiber.