Fiber optic cable power in relay systems

Abstract

The invention discloses fiber optic cable power in a relay system. The optical pumping unit may include a line voltage transistor coupled between an input side and an output side of the optical pumping unit. The optical pump may also include a DC-DC converter having an input side coupled to the line voltage transistor; an optical pump assembly coupled to an output side of the DC-DC converter; a current control accessory coupled to the light pump accessory; a throttle return control fitting having an output coupled to the current control fitting; and a current / voltage sensor for monitoring line current and voltage drop in the optical repeater and coupled to the input of the throttle return control fitting. Accordingly, the throttle return control accessory may be configured to send a signal to the current control accessory to reduce power at the light pump accessory when a drop in the line current or voltage drop occurs.

Description

[0001] Related Applications

[0002] This application claims priority to U.S. Provisional Patent Application Serial No. 63 / 608,519, filed on December 11, 2023, entitled "FIBER OPTIC CABLE POWER IN REPEATERED SYSTEMS", the entire content of which is incorporated herein by reference. Technical Field

[0003] Embodiments of the present disclosure relate to the field of optical communication systems. More specifically, the present disclosure relates to architectures in undersea repeaters for improving power usage in a repeatered undersea communication system. Background Art

[0004] Long-haul optical communication systems, such as undersea optical communication systems, can include a number of interconnected optical cables to facilitate the communication of data and information. For long-haul transmission, such as hundreds or thousands of kilometers, optical communication systems are equipped with devices called repeaters. Repeaters can be placed at intervals of 50 km, 100 km, etc. and include components for amplifying optical signals. Power can be supplied to the optical communication components including the repeaters via wires or cables that can send high-voltage DC current along the undersea communication route.

[0005] In particular, at a given repeater, an optical pump unit (OPU) is powered to generate amplification of the optical signal transmitted through the optical cable. The optical pump unit can control the operation of an erbium-doped fiber amplifier (EDFA) that is used to amplify the optical signal transmitted through the given repeater. The optical pump unit includes circuitry for controlling the operation of the pump lasers used in the EDFA to provide optical amplification.

[0006] An ongoing problem with optical repeaters is the need to efficiently power the EDFA, especially in long-haul systems that can include dozens of repeaters across cable spans.

[0007] It is with reference to these and other considerations that the present disclosure is provided. Summary of the Invention

[0008] In one embodiment, an optical pump unit for an optical repeater is provided. The optical pump unit may include a line voltage transistor coupled between an input side and an output side of the optical pump unit. The optical pump unit may further include a DC-DC converter having an input side coupled to the line voltage transistor, an optical pump fitting coupled to an output side of the DC-DC converter, and a current control fitting coupled to the optical pump fitting. The optical pump unit may further include a throttle valve feedback control fitting having an output coupled to the current control fitting, and a current / voltage sensor for monitoring the line current and voltage drop in the optical repeater and coupled to an input of the throttle valve feedback control fitting. Thus, when a reduction in line current or voltage drop occurs, the throttle valve feedback control fitting may be configured to send a signal to the current control fitting to reduce the power at the optical pump fitting.

[0009] In another embodiment, a system for undersea optical communication is provided. The system may include a station that transmits optical signals through a signal path, a plurality of optical repeaters that amplify the optical signals along the signal path, and a cable that conducts the optical signals along the signal path, the cable including electrical conductors that conduct power to the plurality of optical repeaters. Thus, a given optical repeater among the plurality of optical repeaters may include an erbium-doped fiber and an optical pump unit. The optical pump unit may include a line voltage transistor coupled between an input side and an output side of the optical pump unit, a DC-DC converter having an input side coupled to the line voltage transistor, and an optical pump fitting coupled to an output side of the DC-DC converter. The optical pump unit may further include a current control fitting coupled to the optical pump fitting; a throttle valve feedback control fitting having an output coupled to the current control fitting; and a current and voltage sensor for monitoring the line current and repeater voltage drop in the optical repeater and coupled to an input of the throttle valve feedback control fitting. Thus, the throttle valve feedback control fitting may be configured to send a signal to the current control fitting when a reduction in line current or repeater voltage drop occurs to reduce the power at the optical pump fitting. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A block diagram of an undersea optical communication system arranged in accordance with an embodiment of the present disclosure is shown; and

[0011] Figure 2 A block diagram of an optical pump unit arranged in accordance with an embodiment of the present disclosure is shown; and

[0012] Figure 3 A schematic circuit arrangement of an optical pump unit arranged in accordance with an embodiment of the present disclosure is presented. DETAILED DESCRIPTION

[0013] The present embodiment will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments are shown. The scope of the embodiments should not be construed as limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the embodiments to those skilled in the art. In the drawings, the same numerals always refer to the same elements.

[0014] The present embodiment provides an architecture and components of a subsea communication system. More specifically, it provides an architecture of a repeater optical pump unit that controls the operation of an EDFA, which is used to amplify optical signals transmitted through an optical cable of the subsea communication system.

[0015] Figure 1 A block diagram of a subsea optical communication system (shown as system 100) arranged according to an embodiment of the present disclosure is shown. System 100 can be arranged for two-way communication and can include a terrestrial facility for generating and guiding optical communication signals, receiving optical communication signals, providing electrical power to operate the components of system 100, and other functions known in the art. In Figure 1 the illustration, stations 102A and 102B are shown, and these stations can represent terrestrial facilities located at opposite ends of the subsea system. In some examples, system 100 can have a system length 101 spanning 1000 km, 5000 km, or up to 10000 km or more between stations 102A and 102B, and can be divided into multiple spans 120, such as spans 120A, 120B, … span 120N-1, and span 120N as shown. Note that in a system with a length of 10000 km, the span length can be approximately 100 km, and system 100 can include dozens of spans. The link between stations 102A and 102B is spanned by an optical communication cable 140, which can conduct optical signals transmitted from station 102A along signal path 104 from west to east, where “west” and “east” are only used to indicate opposite ends of system 100. Similarly, cable 140 can conduct optical signals transmitted from station 102B along signal path 106 from east to west. Although not shown separately, multiple optical fibers will be included in cable 140 to provide a conductive path for transmitting optical signals between stations 102A and 102B. Cable 140 can include electrical conductors 148 (such as copper wires) that power multiple optical repeaters, which are used to power the components along system 100. The optical repeaters are in Figure 1are respectively represented as repeater 130A, repeater 130B, repeater 130N-1, and repeater 130N, where the total number N of repeaters can be dozens. In a given repeater, power is required to drive an optical pump unit that amplifies the optical signal conducted along system 100. The system voltage required to operate all components of system 100 is mainly determined by the sum of the voltage drop along the length of cable 140 itself and the total voltage drop across all repeaters 130. In some examples, the system voltage can be in the range of 20 kV or higher.

[0016] As Figure 1 Further shown, the optical pump unit can be included in a given repeater, where the optical pump units (OPUs) are respectively labeled as OPU 150A, OPU 150B, OPU 150N-1, and OPU 150N. Each of these OPUs can include an optical pump based on a semiconductor laser (not shown separately), where a given OPU provides circuitry to more effectively manage the power required to drive the optical pump and associated circuitry. In various embodiments of the present disclosure, as Figure 1 shown, one or more OPUs (e.g., each of the OPUs) can have an architecture as described in the following embodiments, where circuitry and components are provided to more effectively manage the power used by a given repeater.

[0017] Figure 2 A block diagram of an optical pump unit arranged according to an embodiment of the present disclosure is shown. The optical pump unit 200 or OPU 200 can be regarded as a variant of OPU 150. OPU 200 can include a line voltage transistor 202 coupled between the input side IN and the output side OU of OPU 200. The line voltage transistor 202 can set the voltage drop of OPU 200. The optical pump unit 200 can also include a DC-DC converter 204 whose input side is coupled to the line voltage transistor 202 and an optical pump fitting 208 coupled to the output side of the DC-DC converter 204. In the shown embodiment, the optical pump fitting 208 can include a pair of optical pumps (or more than two optical pumps in some variants), shown as optical pump 208A and optical pump 208B. The optical pump fitting 208 can provide a pair of optical pumps to provide redundancy in a given repeater. In addition, OPU 200 can include a current control fitting 210 coupled to the optical pump fitting 208. In the shown example, the current control fitting 210 can include current controllers 210A and 210B respectively coupled to the optical pump 208A and the optical pump 208B. OPU 200 can also include a throttle feedback control fitting 214 whose output is coupled to the current control fitting 210.

[0018] As Figure 2As further shown in, the OPU 200 may include a DAC 212 and a line current / voltage sensor 206. According to an embodiment of the present disclosure, the voltages of the line voltage transistor 202 and the DC-DC converter 204 are optimized to reduce power consumption in the OPU 200, as described in detail below with reference to Figure 3 The circuit of the OPU 200 is arranged such that the pump power is maintained at the nominal line current and above. The line current / voltage sensor 206 may be arranged to monitor the line current and the repeater voltage drop in an optical repeater (see repeater 130), and is coupled to the input of the throttle back control fitting 214, where the throttle back control fitting 214 is configured to send a signal to the current control fitting 210 to reduce the power of the optical pump fitting 208 when a line current reduction occurs. Thus, when the line current or the repeater voltage drops, the power is throttled back to prevent a voltage collapse in the OPU 200.

[0019] Figure 3 A schematic circuit arrangement of an optical pump unit 200A arranged according to an embodiment of the present disclosure is presented. The OPU200A may be regarded as a variant of the above-described OPU 200. The line voltage transistor 202 is implemented as a field effect transistor, and each of the optical pumps 208A and 208B is implemented as a pair of laser diodes providing bidirectional optical pumping for amplifying the signals transmitted on the signal path 104 or the signal path 106.

[0020] The current control fitting 210 in this embodiment is formed by a pair of current control transistors labeled Q3 and Q4, where the first current control transistor (Q3) is connected to the first optical pump (optical pump 208A) of the optical pump fitting 208, and the second current control transistor (Q4) is separately connected to the second optical pump (optical pump 208B) of the optical pump fitting 208. The throttle back control fitting 214 of the optical pump unit 150A may include a pair of comparison circuits, where the first comparison circuit (U6 and U7) is connected to the first current control transistor (Q3), and the second comparison circuit (U8 and U9) is separately connected to the second current control transistor (Q4).

[0021] As Figure 3 further described in, the optical pump unit 200A may include a surge voltage diode 220, which is coupled between the input side and the output side of the optical repeater including the OPU 200A. The optical pump unit 200A may also include a shunt voltage circuit 222 coupled between the input side and the output side of the optical repeater.

[0022] Some general advantages of the above embodiments are providing adjustability of the voltage drop. Note that undersea optical communications can generally be designed to accommodate the worst-case fiber pairs in the system that cause the total system voltage to be too large. The setting of the line voltage transistor 202 allows the repeater voltage drop to be much smaller than in prior art systems, resulting in potentially significant power savings.

[0023] Experimental data

[0024] A simulation of an undersea optical communication system was performed on a 10,000 km long cable with 144 bidirectional repeaters to determine the values of various operating parameters. For a known system with repeaters having known OPUs arranged, the simulated nominal line current value was 0.783 A, the repeater voltage drop was 60.8 V, the total system voltage was 20.5 kV, and the total system power was 16.0 kW. For a system with a set of OPUs of this embodiment arranged, the nominal line current was 0.625, and the average repeater voltage drop was 51.1 V, the total system voltage was 17.0 kV, and the total system power was 10.6 kW. Thus, in this one non-limiting example, a system with OPUs 150, 200 may require a lower system voltage and can save 34% in power.

[0025] The scope of the present disclosure is not limited to the specific embodiments described herein. In fact, various other embodiments and modifications of the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and the accompanying drawings. Accordingly, these other embodiments and modifications are intended to fall within the scope of the present disclosure. Moreover, although the present disclosure is described herein in the context of a particular implementation for a particular purpose in a particular environment, those of ordinary skill in the art will recognize that its usefulness is not limited thereto, and the present disclosure can be advantageously used in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in view of the full scope, breadth, and spirit of the present disclosure as described herein.

Claims

1. An optical pump unit for an optical repeater, comprising: a line voltage transistor coupled between an input side and an output side of the optical pump unit; a DC-DC converter having an input side coupled to the line voltage transistor; an optical pump accessory coupled to an output side of the DC-DC converter; a current control assembly coupled to the optical pump assembly; a throttle return control accessory having an output coupled to the current control accessory; and A current / voltage sensor for monitoring line current and voltage drop in the optical repeater and coupled to an input of the throttle feedback control accessory, wherein the throttle feedback control accessory is configured to send a signal to the current control accessory to reduce power at the optical pump accessory when a decrease in line current or voltage drop occurs.

2. The optical pump unit according to claim 1, wherein: The optical pump assembly comprises at least two optical pumps, wherein each of the at least two optical pumps is arranged as a bidirectional optical pump.

3. The optical pump unit according to claim 2, wherein the current control accessory comprises a pair of current control transistors, wherein a first current control transistor is connected to a first optical pump of the optical pump accessory, and a second current control transistor is separately connected to a second optical pump of the optical pump accessory.

4. The optical pump unit according to claim 3, wherein: The throttle valve feedback control accessory includes a pair of comparison circuits, wherein a first comparison circuit is connected to the first current control transistor and a second comparison circuit is connected solely to the second current control transistor. 5 . The optical pump unit according to claim 1 , further comprising a surge voltage diode coupled between an input side and an output side of the optical repeater. 6 . The optical pump unit of claim 1 , further comprising a shunt voltage circuit coupled between an input side and an output side of the optical repeater.

7. A system for submarine optical communications, comprising: a station for transmitting an optical signal on a signal path; a plurality of optical repeaters for amplifying the optical signal along the signal path; a cable for conducting the optical signal along the signal path, the cable comprising electrical conductors for conducting power to the plurality of optical repeaters, wherein a given optical repeater of the plurality of optical repeaters comprises: Erbium-doped optical fiber; and Optical pump unit, comprising: a line voltage transistor coupled between an input side and an output side of the optical pump unit; a DC-DC converter having an input side coupled to the line voltage transistor; an optical pump accessory coupled to an output side of the DC-DC converter; a current control assembly coupled to the optical pump assembly; a throttle return control accessory having an output coupled to the current control accessory; and A current and voltage sensor for monitoring line current and repeater voltage drop in the optical repeater and coupled to an input of the throttle feedback control accessory, wherein the throttle feedback control accessory is configured to send a signal to the current control accessory to reduce power at the optical pump accessory when a decrease in line current or repeater voltage drop occurs.

8. The system according to claim 7, wherein: The optical pump assembly comprises a pair of optical pumps, wherein each optical pump of the pair of optical pumps is arranged as a bidirectional optical pump.

9. The system of claim 8, wherein the current control accessory comprises a pair of current control transistors, wherein a first current control transistor is connected to a first optical pump of the optical pump accessory, and a second current control transistor is separately connected to a second optical pump of the optical pump accessory.

10. The system of claim 9, wherein the throttle feedback control assembly includes a pair of comparison circuits, wherein a first comparison circuit is connected to the first current control transistor and a second comparison circuit is separately connected to the second current control transistor.

11. The system of claim 7, further comprising a surge voltage diode coupled between an input side and an output side of the optical repeater.

12. The system of claim 7, further comprising a shunt voltage circuit coupled between an input side and an output side of a given optical repeater.

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