Passive optical communication network with broadband upgrade

Abstract

An optical communication network includes at least one single-mode fiber, referred to as a "primary fiber," for transmission between a central office and a distribution node, and at least one multiplicity of single-mode fibers, referred to as "distribution fibers," for transmission between the distribution node and a multiplicity of optical network units (ONUs). Transmissions are exchanged between the primary and distribution fibers via at least one optical coupler located at the distribution node. The network is passive in the sense that all monitoring of the transmission media and the ONUs can be performed at the central office, without active intervention at remote locations. The network includes a monitor and a multiplicity of bypass lines by means of which at least a portion of inbound signals from the distribution fibers are transmitted to the monitor without passing through the optical coupler at the distribution node.

I claim: .[. 
     
       1.  An optical communication system which comprises: first means for generating optical signals within a first wavelength band; second means for generating optical signals lying within at least some of N mutually disjoint wavelength sub-bands, N an integer greater than 1, the N sub-bands collectively lying within a second wavelength band disjoint from the first wavelength band; and at least one passive optical network, to be referred to as a PON, for conveying optical signals from the first and second generating means to N optical network units, to be referred to as ONUs at terminal locations, the PON comprising: a) a primary fiber optically coupled to the first and second generating means;   b) a plurality of distribution fibers each optically coupled to a respective ONU or group of ONUs;   c) means, to be referred to as a splitter, for passively splitting at least some primary-fiber transmissions into the plurality of distribution fibers;   d) means for optically coupling first-wavelength-band signals into the primary fiber;   e) means for optically coupling second-wavelength-band signals into the primary fiber such that first-band and seconded signals can be simultaneously coupled, and such that two or more sub-band signals can be simultaneously coupled;   f) first wavelength-selective means to be referred to as a first WDM, optically coupled to the primary fiber and to the splitter, the first WDM adapted to divert second-band signals such that the second-band signals are prevented from entering the splitter from the primary fiber, but first-band signals are permitted to enter the splitter from the primary fiber;   g) bypass means for optically coupling second-band sign a s diverted by the first WDM, into the distribution fibers without said second-band signals passing through the splitter; and   h) second wavelength-selective means, to be referred to as a second WDM, included in the bypass means, the second WDM adapted to couple optical signals lying in each sub-band or predetermined group of sub-bands exclusively into a distribution fiber associated with that sub-band or group..].   
     
     
       2. .[.The system of claim 1, wherein the PON further comprises, associated with at least one of the distribution fibers, M sub-distribution fibers, M an integer greater than 1, and the PON further comprises:.]. .Iadd.An optical communication system which comprises: first means for generating optical signals within a first wavelength band; second means for generating optical signals lying within at least some of N mutually disjoint wavelength sub-bands, N an integer greater than 1, the N sub-bands collectively lying within a second wavelength band disjoint from the first wavelength band; and at least one passive optical network, to be referred to as a PON, for conveying optical signals from the first and second generating means to N optical network units, to be referred to as ONUs, at terminal locations, the PON comprising: a) a primary fiber optically coupled to the first and second generating means;   b) a plurality of distribution fibers, each optically coupled to a respective ONU or group of ONUs;   c) means, to be referred to as a splitter, for passively splitting at least some primary-fiber transmissions into the plurality of distribution fibers;   d) means for optically coupling first-wavelength-band signals into the primary fiber;   e) means for optically coupling second-wavelength-band signals into the primary fiber such that first-band and second-band signals can be simultaneously coupled, and such that two or more sub-band signals can be simultaneously coupled;   f) first wavelength-selective means, to be referred to as a first WDM, optically coupled to the primary fiber and to the splitter, the first WDM adapted to divert second-band signals such that the second-band signals are prevented from entering the splitter from the primary fiber, but first-band signals are permitted to enter the splitter from the primary fiber;   g) bypass means for optically coupling second-band signals, diverted by the first WDM, into the distribution fibers without said second-band signals passing through the splitter;   h) second wavelength-selective means, to be referred to as a second WDM included in the bypass means, the second WDM adapted to couple optical signals lying in each sub-band or predetermined group of sub-bands exclusively into a distribution fiber associated with that sub-band or group;   i) associated with at least one of the distribution fibers, M sub-distribution fibers, M an integer greater than 1; .Iaddend.   .[.a.]. .Iadd.j.Iaddend.) means to be referred to as a sub-splitter, for passively splitting at least some transmissions from the distribution fiber into the sub-distribution fibers;   .[.b.]. .Iadd.k.Iaddend.) third wavelength-selective means, to be referred to as a third WDM, for diverting second-band signals such that the second-band signals are prevented from entering the sub-splitter from the distribution fiber, but first-band signals are permitted to enter the sub-splitter from the distribution fiber;   .[.c.]. .Iadd.l.Iaddend.) means, to be referred to as sub-bypass means, for optically coupling second-band signals, diverted by the third WDM, into the sub-distribution fibers without said second-band signals passing through the sub-splitter; and   .[.d.]. .Iadd.m.Iaddend.) fourth wavelength-selective means, to be referred to as a fourth WDM, included in the sub-bypass means, the fourth WDM adapted to couple optical signals lying in each sub-band exclusively into a sub-distribution fiber associated with that sub-band.   
     
     
       3. .[.The system of claim 1, wherein the PON for conveying optical signals from the generating means to the ONUs, to be referred to as an outbound PON, is adapted for unidirectional transmission, and the system further comprises:.]. .Iadd.An optical communication system which comprises: first means for generating optic signals within a first wavelength band; second means for generating optical signals lying within at least some of N mutually disjoint wavelength sub-bands, N an integer greater than 1, the N sub-bands collectively lying within a second wavelength band disjoint from the first wavelength band; and at least one passive optical network adapted for unidirectional transmission, to be referred to as an outbound PON, for conveying optical signals from the first and second generating means to N optical network units, to be referred to as ONUs, at terminal locations, the outbound PON comprising: a) a primary fiber optically coupled to the first and second generating means;   b) a plurality of distribution fibers, each optically coupled to a respective ONU or group of ONUs;   c) means, to be referred to as a splitter, for passively splitting at least some primary-fiber transmissions into the plurality of distribution fibers;   d) means for optically coupling first-wavelength-band signals into the primary fiber;   e) means for optically coupling second-wavelength-band signals into the primary fiber such that first-band and second-band signals can be simultaneously coupled, and such that two or more sub-band signals can be simultaneously coupled;   f) first wavelength-selective means, to be referred to as a first WDM, optically coupled to the primary fiber and to the splitter, the first WDM adapted to divert second-band signals such that the second-band signals are prevented from entering the splitter from the primary fiber, but first-band signals are permitted to enter the splitter from the primary fiber;   g) bypass means for optically coupling second-band signals, diverted by the first WDM, into the distribution fibers without said second-band signals passing through the splitter; and   h) second wavelength-selective means, to be referred to as a second WDM, included in the bypass means, the second WDM adapted to couple optical signals lying in each sub-band or predetermined group of sub-bands exclusively into a distribution fiber associated with that sub-band or group;   wherein the optical communication system further comprises: .Iaddend.   .[.a.]. .Iadd.i.Iaddend.) first means for detecting first-band signals and second means for detecting second-band signals;   .[.b.]. .Iadd.j.Iaddend.) an inbound PON for conveying optical signals from the ONUs toward the first and second detecting means, the inbound PON being adapted for unidirectional transmission, and the inbound PON including an inbound primary fiber;   .[.c.]. .Iadd.k.Iaddend.) means for optically coupling first-wavelength-band signals from the inbound primary fiber into the first detecting means; and   .[.d.]. .Iadd.l.Iaddend.) means for optically coupling second-wavelength-band signals from the inbound primary fiber into the second detecting means such that first-band and second-band signals can be simultaneously detected, and such that two or more sub-band signals can be simultaneously detected. .[.4. The system of claim 1, further comprising:   a) third means for generating optical signals lying within a third wavelength band disjoint from the first and second wavelength bands; and   b) means for optically coupling third-band signals into the primary fiber such that first-band, second-band, and third-band signals can be   
     
     
        simultaneously coupled..].5. .[.The system of claim 4, further comprising:.]. .Iadd.An optical communication system which comprises: first means for generating optical signals within a first wavelength band; second means for generating optical signals lying within at least some of N mutually disjoint wavelength sub-bands, N an integer greater than 1, the N sub-bands collectively lying within a second wavelength band disjoint from the first wavelength band; and at least one passive optical network, to be referred to as a PON, for conveying optical signals from the first and second generating means to N optical network units, to be referred to as ONUs, at terminal locations, the PON comprising: a) a primary fiber optically coupled to the first and second generating means;   b) a plurality of distribution fibers, each optically coupled to a respective ONU or group, of ONUs;   c) means, to be referred to as a splitter, for passively splitting at least some primary-fiber transmissions into the plurality of distribution fibers;   d) means for optically coupling first-wavelength-band signals into the primary fiber;   e) means for optically coupling second-wavelength-band signals into the primary fiber such that first-band and second-band signals can be simultaneously coupled, and such that two or more sub-band signals can be simultaneously coupled;   f) first wavelength-selective means, to be referred to as a first WDM, optically coupled to the primary fiber and to the splitter, the first WDM adapted to divert second-band signals such that the second-band signals are prevented from entering the splitter from the primary fiber, but first-band signals are permitted to enter the splitter from the primary fiber;   g) bypass means for optically coupling second-band signals, diverted by the first WDM, into the distribution fibers without said second-band signals passing through the splitter; and   h) second wavelength-selective means, to be referred to as a second WDM, included in the bypass means, the second WDM adapted to couple optical signals lying in each sub-band or predetermined group of sub-bands exclusively into a distribution fiber associated with that sub-band or group;   wherein the optical communication system further comprises:   i) third means for generating optical signals lying within a third wavelength band disjoint from the first and second wavelength bands;   j) means for optically coupling third-band signals into the primary fiber such that first-band, second-band, and third-band signals can be simultaneously coupled; .Iaddend.   .[.a.]. .Iadd.k.Iaddend.) an optical fiber amplifier having an input end optically coupled to the primary fiber and an output end optically coupled to the splitter, the optical fiber amplifier being adapted to amplify third-band signals; and   .[.b.]. .Iadd.l.Iaddend.) wavelength-selective means for separating first-band signals from third-band signals such that first-band signals are optically coupled into the splitter without passing through the   
     
     
        optical amplifier. 6. The system of claim 5, wherein the first, second, and third generating means are situated at a central office, the amplifier is situated at a location remote from the central office, and the system further comprises: a) a source of electromagnetic radiation for pumping the amplifier, said source situated at the central office, and   b) means for coupling radiation from the source into the primary fiber.   
     
     
        .Iadd.7.  A passive optical network (PON) having at least one input port at a central location and a plurality of output ports, wherein: said PON is responsive to input optical signals in a first wavelength region for routing said first-wavelength-region signals from the central location to respective individual output ports for reception at remote locations according to particular wavelengths of said signals within the first wavelength region, and the PON is responsive to input optical signals in a second wavelength region disjoint from said first wavelength region, for routing a portion of each of said second-wavelength-region signals into each of the output ports for reception at said remote locations,   CHARACTERIZED IN THAT   the PON is responsive to input optical signals in a third wavelength region for routing said third-wavelength-region signals from the central location to the output ports, and for returning backscattered portions of said third-wavelength-region signals to a monitor at the central location.   
     
     
        .Iaddend..Iadd.8.  The passive optical network of claim 7, comprising: a passive optical splitting element for distributing second-wavelength-region signals into the output ports; and a passive optical wavelength-dividing element for routing at least first-wavelength-region signals to respective output ports according to wavelength. .Iaddend..Iadd.9. The passive optical network of claim 8, wherein said passive optical splitting element is effective for routing third-wavelength-region signals, at least from the central location to the remote locations, according to wavelength. .Iaddend..Iadd.10. The passive optical network of claim 8, comprising a further passive optical splitting element for routing third-wavelength-region signals, at least from the central location to respective remote locations, according to wavelength. .Iaddend..Iadd.11. The passive optical network of claim 7, wherein said PON is responsive to signals in at least one wavelength region for routing said signals from input ports at the respective remote locations to an 
     
     
        output port at the central location. .Iaddend..Iadd.12.  The passive optical network of claim 11, where at least one port at the central location is effective as both an input port and an output port, and at least one port at each remote location is effective as both an input port and an output port. .Iaddend.