High power line system for hollow core optical

Abstract

A system for transmitting optical signals between a first solid core optical fiber network and a hollow core optical fiber network, the system comprising a plurality of transponder-amplifiers, where each transponder-amplifier of the plurality of transponder-amplifiers comprises a transponder in optical communication with one of a power amplifier and a preamplifier. A plurality of transponder-amplifiers are in optical communication with the first solid fiber network and are configured to receive a plurality of first optical signals from the plurality of transponder-amplifiers. A multiplexer downstream of the plurality of transponder-amplifiers is used to receive a plurality of first optical signals. And a multiplexer for selecting between the plurality of first optical signals and transmitting at least one of the plurality of first optical signals to the air-core optical fiber network.

Description

High-power circuit systems for hollow optical fibers and their applications Background Technology

[0001] Long-distance, terrestrial fiber optic networks connect cities and countries worldwide. These networks typically span hundreds to thousands of kilometers and have largely migrated to 100G (100Gbps) dense wavelength division multiplexing (DWDM) systems with 80 or more channels. Typically, optical fibers with solid waveguide cores are used, configured for single-mode (single-mode fiber or SM fiber) or multi-mode (multi-mode fiber or MM fiber) propagation. An example of single-mode or multi-mode fiber is silica fiber carrying optical signals at a wavelength of approximately 1550 nm, where silica has the lowest loss, allowing signals to propagate over long distances with minimal attenuation. Fibers used to carry data signals can be encapsulated in cables that include one or more fibers within an outer sheath that protects the fiber during deployment and use.

[0002] Within metropolitan areas and wide area networks (WANs), cloud service providers (CSPs) typically offer high bandwidth with near-perfect service availability and appropriate latency to meet customers' needs for various types of data, including enterprise cloud applications and email, Voice over Internet Protocol (VoIP), streaming video, the Internet of Things (IoT), search, and cloud storage. Data centers are distributed throughout the metropolitan area and interconnected via optical transmission systems. These clusters of data centers within the metropolitan area are referred to as metropolitan area zones or metropolitan area rings.

[0003] One drawback of this conventional network system is its power limitation. Since all input signals are amplified by a single amplifier before being transmitted to the network, the amplifier's power capability determines the network's data transmission capacity. Because amplifiers with greater power capabilities can transmit optical signals over greater ground distances, it also determines the network size.

[0004] Another drawback of this type of network system is that the failure of any active component (such as a line amplifier or preamplifier) ​​can lead to a large-scale system failure across the entire network, because each amplifier acts as a gateway to the entire network system. Therefore, the failure of any single active component can create a large "blast radius" (e.g., affecting a large number of customers). For example, the failure of a single active component could temporarily render a network in a large city inoperable. Summary of the Invention

[0005] In one embodiment, a system for transmitting optical signals between a first solid-core fiber network and a hollow-core fiber network includes a plurality of transponder-amplifiers, each of the plurality of transponder-amplifiers including a transponder that optically communicates with one of a power amplifier and a preamplifier. The plurality of transponder-amplifiers optically communicate with the first solid-core fiber network and are used to receive a plurality of first optical signals from the plurality of transponder-amplifiers. A multiplexer located downstream of the plurality of transponder-amplifiers is used to receive the plurality of first optical signals. The multiplexer is used to select among the plurality of first optical signals and transmit at least one of the plurality of first optical signals to the hollow-core fiber network.

[0006] In another embodiment, a method for transmitting optical signals between a solid-core fiber network and a hollow-core fiber network includes transmitting a plurality of first optical signals from the solid-core fiber network to a plurality of transponder-amplifiers. Each of the plurality of transponder-amplifiers includes a transponder that optically communicates with a power amplifier and a preamplifier. The plurality of first optical signals are amplified using the power amplifier. A multiplexer located downstream of the plurality of transponder-amplifiers selects among the plurality of first optical signals received from the plurality of transponder-amplifiers and transmits at least one of the plurality of first optical signals to the hollow-core fiber network. Attached Figure Description

[0007] Figure 1 is a schematic diagram of a conventional transceiver amplifier, which communicates optically with the hollow fiber on the transmitter side and the hollow fiber on the receiver side of the amplifier.

[0008] Figure 2 is a schematic diagram of a network system using the conventional amplifier in Figure 1;

[0009] Figure 3 is an exemplary depiction of a network system that includes distributed line amplification and pre-amplification combined with repeaters; and

[0010] Figure 4 is an exemplary depiction of the multiplexer of Figure 3, in which the line amplifier and preamplifier are excluded from the design. Detailed Implementation

[0011] This paper discloses a system comprising a multiplexer-demultiplexer (hereinafter referred to as the "multiplexer") for optical communication with transponders, wherein the transponders are integrated with active amplifier components. These active components are removed from separate conventional amplifiers used as gateways to the entire network and redistributed and integrated with individual transponders to form transponder-amplifier combinations (hereinafter referred to as transponder-amplifiers). The transponder-amplifiers are used to transmit signals from a solid-core fiber network to a hollow-core fiber network. The distribution and integration of these active amplifier components with the individual transponders (to form transponder-amplifiers) increases the reliability and robustness of the network by reducing the probability that the failure of a single active component would render the entire network inoperable.

[0012] This redistribution disperses the vulnerable active components in the system. Therefore, a failure of a single line amplifier or preamplifier only causes the failure of that specific repeater and does not render the entire network temporarily inoperable. Because only that part of the network is affected, the "blast radius" (i.e., the number of customers affected by the change) is reduced. The rest of the network can continue to operate unaffected by the failure.

[0013] Furthermore, transponder-amplifier combinations allow for the use of different types of amplifiers for different circuits. Because multiple amplifiers can be used, amplifier saturation can be minimized and overall system power can be increased. Saturation output power is the maximum output power obtainable from the amplifier.

[0014] As mentioned above, repeater-amplifier combinations are used to facilitate data transmission from solid-core fiber networks to hollow-core fiber networks. By guiding light through air rather than glass, hollow-core fiber provides an alternative to conventional solid-core fiber. This enables data transmission at near-vacuum speeds of light and higher optical power over wider optical bandwidths, without issues such as nonlinearity and thermo-optical effects that can affect light waves propagating in solids. Compared to solid-core fiber, hollow-core fiber exhibits lower latency over longer distances and requires fewer repeaters.

[0015] While hollow fiber offers significant advantages over solid fiber, these advantages remain largely untapped because the rest of the existing infrastructure for data transmission is still based on solid fiber. Examples of this can be seen in Figures 1 and 2. Figure 1 is a schematic depiction of a conventional transceiver amplifier 100 that optically communicates with hollow fiber 200 on the transmitter side and hollow fiber 400 on the receiver side of the amplifier 100. Figure 2 is an exemplary depiction of a network system 500 using the conventional amplifier 100 of Figure 1. Both hollow fiber 200 and hollow fiber 400 optically communicate with a hollow fiber network (not shown).

[0016] A conventional amplifier 100 transmits data from multiple solid optical fibers (not shown) to a hollow optical fiber 200 on the transmitter side, and from the hollow optical fiber 400 to multiple solid optical fibers (not shown) on the receiver side. The transmitter side of the amplifier 100 includes multiple input connectors 102 for contacting the multiple solid optical fibers (not shown), which transmit data to the hollow optical fiber 200 in the form of optical signals. The receiver side of the amplifier transmits data from the hollow optical fiber 400 to multiple output receiver connectors 420 that communicate with the multiple solid optical fibers.

[0017] The transmitter side of amplifier 100 includes multiple input connectors 102 for contacting multiple solid optical fibers (not shown), which transmit data to multiplexer 104 in the form of optical signals. Multiplexer 104 is located upstream of a first beam splitter 106 that optically communicates with an optical channel monitor (OCM) 109. Multiplexer 104 optically communicates with the multiple input connectors 102 and uses wavelength division multiplexing (WDM) to select among multiple inputs received from the multiple solid optical fibers contacting the multiple input connectors 102. WDM involves multiplexing multiple optical signals onto a first single optical fiber 105 using lasers of different wavelengths (i.e., colors).

[0018] The optical signal extracted from the first single fiber 105 by the beam splitter 106 allows the optical channel monitor 109 to measure the optical transmission signal data. An optical line amplifier 108, located downstream of the beam splitter, amplifies the optical signal to 37 to 51 dBm. The line amplifier is an erbium-doped fiber amplifier (EDFA). The EDFA can be optically coupled to two laser diodes (LDs) (not shown), which provide pump power for laser amplification via stimulated emission.

[0019] Downstream of the optical line amplifier 108 is an optical time reflectometer (OTDR) 114, which communicates with the first single optical fiber 105 via coupler 110 and beam splitter 112. The OTDR measures backscattered light from the fiber to identify any loss or fault in the fiber network. Downstream of the OTDR is an optical monitoring channel (OSC) 120, which communicates with the first single optical fiber 105 via optical coupler 122. The OSC provides continuous monitoring capabilities, allowing real-time monitoring of the amplifier's performance. The first single optical fiber 105 communicates optically with an output connector 124, which in turn communicates with a hollow-core optical fiber 200.

[0020] On the receiver side of amplifier 100, hollow fiber 400 contacts input connector 402, which in turn contacts second single fiber 405. Downstream of input connector 402 are beam splitter 404 for optical communication with OSC 120, optical coupler 406 and beam splitter 410 for optical communication with OTDR 114, and preamplifier 412 located downstream of all beam splitters 404, 408, and 410. Preamplifier 412 is positioned upstream of demultiplexer 416 such that sufficient optical power is received by demultiplexer 416 and transmitted to multiple output receiver connectors 420. Demultiplexer 416 takes the input optical signal from second single fiber 405 and then switches it sequentially to any one of the multiple individual output lines. Demultiplexer 416 can convert a serial optical signal received from preamplifier 412 into a parallel data stream, wherein each data stream can be directed to each of a plurality of solid optical fibers that are in contact with a plurality of output receiver connectors 420.

[0021] The amplifier 100 in Figure 1 illustrates many drawbacks associated with this data transmission method. These drawbacks are illustrated in conjunction with Figure 2. Figure 2 is a schematic diagram of a network system 500 using the amplifier 100 of Figure 1. Multiple transponders 502A, 502B, ..., 502n and multiple transponders 504A, 504B, ..., 504n are used to transmit and receive optical signals via amplifiers 100A, 100B, and the hollow fiber optic network 600. “n” is an integer. When these transponders are transmitting optical signals, amplifiers 100A and 100B are downstream of the multiple transponders 502A, 502B, ..., 502n, while when these transponders are receiving optical signals, amplifiers 100A and 100B are upstream of the multiple transponders 504A, 504B, ..., 504n. Similarly, when these transponders are receiving optical signals, amplifiers 100A and 100B are located upstream of multiple transponders 502A, 502B, ..., 502n, while when these transponders are transmitting optical signals, amplifiers 100A and 100B are located downstream of multiple transponders 504A, 504B, ..., 504n.

[0022] Amplifiers 100A and 100B each employ the amplifier design depicted in Figure 1 and include the multiplexer, demultiplexer, line amplifier, and preamplifier described above. As shown in Figure 2, each amplifier 100A and amplifier 100B serves as a gateway to the entire network system 500.

[0023] One drawback of this conventional network system 500 is its power limitation. Since all input signals are amplified by a single amplifier (100A or 100B) before being transmitted to the hollow fiber network 600, the power capability of the amplifier determines the network's data transmission capacity. Because amplifiers with greater power capabilities can transmit optical signals over greater ground distances, the power capability of each amplifier also determines the network size.

[0024] Another drawback of network system 500 is that the failure of any active component (such as a line amplifier or preamplifier) ​​in a single amplifier (100A or 100B) can cause a large-scale system failure in the entire hollow fiber network 600, because each amplifier 100A and amplifier 100B serves as a gateway to the entire network system. Therefore, the failure of any single active component in any single amplifier can have a large "blast radius" (e.g., a large number of customers affected by the failure). For example, the failure of a component in either amplifier 100A or amplifier 100B could temporarily render a network in a large city inoperable. This is undesirable.

[0025] One solution to this problem is to have a redundant backup network with redundant amplifiers. However, this is not a cost-effective solution.

[0026] Therefore, it is desirable to use alternative transponder and amplifier designs that do not depend on the continuous long-term operation of a single active component in these devices.

[0027] Figure 3 is a schematic diagram of system 5000, in which inline amplifiers and preamplifiers, typically present in amplifiers (such as those shown in Figure 1), are removed from the amplifiers and redistributed to combine with multiple transponders to form transponder-amplifiers 5020A, 5020B, ..., 5020n. When transmitting optical signals from the first solid fiber network 8000A to the hollow fiber network 6000, these transponder-amplifiers 5020A, 5020B, ..., 5020n are positioned upstream of the multiplexer / demultiplexer 1000A (hereinafter referred to as mux / demux 1000A). Conversely, when transmitting optical signals from the hollow fiber network 6000 to the second solid fiber network 8000B, multiple transponder-amplifiers 5040A, 5040B, ..., 5040n are positioned downstream of the multiplexer / demultiplexer 1000B (hereinafter referred to as mux / demux 1000B). Each of the multiple transponder-amplifiers operates independently of the others. It should be noted that the term multiplexer includes demultiplexer, and vice versa. Therefore, multiplexer 1000A also serves as a demultiplexer for optical signals transmitted from the hollow-core fiber network to either the first solid-core fiber network 8000A or the second solid-core fiber network 8000B. The same logic applies to demultiplexer 1000B; it can also be used as a multiplexer for optical signals propagating in opposite directions.

[0028] As a result of this new configuration, the conventional amplifiers in Figures 1 and 2 primarily function as multiplexers when transmitting optical signals from the first solid fiber network 8000A to the hollow fiber network 6000, and primarily as demultiplexers when transmitting optical signals from the hollow fiber network 6000 to the second solid fiber network 8000B. No amplifiers are used downstream of the multiplexers or upstream of the hollow fiber 6000.

[0029] The operating principle of system 5000 in Figure 3 will now be described in detail. At one end of the hollow-core fiber network 6000, a first plurality of transponder-amplifiers 5020A, 5020B, ..., 5020n receive multiple first optical signals from a first solid-core fiber network 8000A. These first optical signals received at the first plurality of transponder-amplifiers 5020A, 5020B, ..., 5020n are amplified to the desired power before being transmitted to the first mux / demux 1000A for optical communication with the hollow-core fiber network 6000. At the opposite end of the hollow-core fiber network 6000, optical communication is established with a second plurality of transponder-amplifiers 5040A, 5040B, ..., 5040n via a second mux / demux 1000B. The optical signal received by the second mux / demux 1000B is demultiplexed into a second plurality of optical signals, which are transmitted to a second plurality of repeater-amplifiers 5040A, 5040B, ..., 5040n. The second plurality of repeater-amplifiers 5040A, 5040B, ..., 5040n amplify the power of the corresponding optical signals to the value required for transmission through the second solid fiber optic network 8000B.

[0030] As described above, each of the multiple transponder-amplifiers includes a transponder that performs optical communication with a power amplifier and a preamplifier. As shown in Figure 3, each transponder-amplifier 5020A, 5020B, ..., 5020n, 5040A, 5040B, ..., 5040n includes a power amplifier and a preamplifier integrated with the transponder. For example, transponder-amplifier 5020A includes a power amplifier 5021A and a preamplifier 5023A (integrated with a first transponder), while transponder-amplifier 5020B includes a power amplifier 5021B and a preamplifier 5023B (integrated with a second transponder), and so on. While the term power amplifier is used to refer to an amplifier that amplifies the optical signal supplied to the multiplexer, these specific amplifiers can also be line amplifiers that are not conventionally used as power amplifiers. As used herein, the term "power amplifier" includes any amplifier that amplifies the optical signal supplied to the multiplexer and can include conventional power amplifiers as well as line amplifiers such as EDFAs.

[0031] Power amplifiers 5021A, 5021B, ..., 5021n are used to increase the power of multiple first optical signals arriving at transponder-amplifiers 5020A, 5020B, ..., 5020n via a router (not shown) from the first solid fiber optic network 8000A. Each transponder-amplifier accepts input in the form of standard single-mode or multimode laser pulses. The inputs can come from different physical media and different protocols and service types. In this embodiment, power amplifiers 5021A, 5021B, ..., 5021n are enhancement amplifiers that amplify the intensity of the optical signals as they leave their respective transponder-amplifiers 5020A, 5020B, ..., 5020n and proceed to the mux / demux 1000A.

[0032] The wavelength of the input optical signal in a transponder-amplifier is mapped to a WDM or DWDM wavelength by the transponder section of the transponder-amplifier. The optical transponder section of the transponder-amplifier extends the transmission distance by converting the wavelength and amplifying the optical signal. It automatically receives, amplifies, and subsequently retransmits the signal at a different wavelength without changing the data / signal content.

[0033] WDM or DWDM wavelengths from multiple transponder-amplifiers 5020A, 5020B, ..., 5020n are multiplexed by a mux / demux 1000A to form an optical signal that is transmitted into the hollow fiber 6000. The same process occurs in the transponder-amplifiers 5040A, 5040B, ..., 5040n when an optical signal to be transmitted to the hollow fiber 6000 via demultiplexer 1000B is received from the second open network (i.e., the second solid fiber network 8000B). The first solid fiber network 8000A and the second solid fiber network 8000B typically include client-side equipment.

[0034] Optical signals from hollow fiber 6000 are received by mux / demux 1000B, where they are demultiplexed into a second set of optical signals, which are then transmitted to a second set of transponders—amplifiers 5040A, 5040B, ..., 5040n. Preamplifiers 5043A, 5043B, ..., 5043n amplify the power of the second set of optical signals to the value required for transmission through the second solid fiber network 8000B.

[0035] The system 5000 pairs of optical signals transmitted in opposite directions (i.e., from the second solid fiber network 8000B to the first solid fiber network 8000A via the hollow fiber network 6000) operate on the same principle. Before being multiplexed by the mux / demux 1000B, the multiple optical signals received from the second solid fiber network 8000B are first amplified by power amplifiers 5041A, 5041B, ..., 5041n (which are contained in the second plurality of transponder-amplifiers 5040A, 5040B, ..., 5040n). The optical signal emitted from mux / demux 1000B is transmitted to mux / demux 1000A via hollow fiber network 6000. This optical signal is demultiplexed into multiple optical signals amplified in preamplifiers 5023A, 5023B, ..., 5023n (included in the first plurality of transponder-amplifiers 5020A, 5020B, ..., 5020n). The preamplifiers 5023A, 5023B, ..., 5023n amplify the power of the multiple optical signals to the value required for transmission through the first solid fiber network 8000A.

[0036] The preamplifiers 5023A, 5023B, ..., 5023n, located in the respective transponder-amplifier sections, amplify the signal after mapping the wavelength to the desired output type and transmitting it to the first open network 8000A. The same process occurs in the transponder-amplifiers 5040A, 5040B, ..., 5040n when the optical signal is to be transmitted from the hollow fiber 6000 to the second open network 8000B.

[0037] The amplifiers included in each of the repeater-amplifiers will now be described in detail. In embodiments, each repeater-amplifier 5020A, 5020B, ..., 5020n, 5040A, 5040B, ..., 5040n may contain power amplifiers or preamplifiers that are the same as each other (in terms of power amplification capability) or different from each other. In other words, the power amplifiers and preamplifiers may both have the same power rating or different power ratings. In embodiments, some of the power amplifiers and some of the preamplifiers may be the same as each other, while the remaining power amplifiers and preamplifiers may be different from each other. Depending on the design of the repeater-amplifier, the power amplifier may be a boost amplifier, a line amplifier, or a cascaded line amplifier. The power amplifier can be a Raman amplifier, a semiconductor optical amplifier, a tapered amplifier, an optical parametric amplifier, a regenerative amplifier, an ultrafast amplifier, a master oscillator power amplifier, a chirped-pulse amplifier, a split-pulse amplifier, a line amplifier including erbium-doped (Er), ytterbium-doped (Yb), and praseodymium-doped (Pr) fiber amplifiers, or a combination thereof.

[0038] In an embodiment, if different amplifiers are deployed in different transponder-amplifiers of system 5000, the individual optical signals received in the different transponder-amplifiers can be amplified to different power levels by different mechanisms. For example, the amplification mechanism and the amplified power level of the first optical signal from a first transponder-amplifier in a first transponder-amplifier may be different from that of the second optical signal from a second transponder-amplifier.

[0039] Since the system 5000 of Figure 3 can contain multiple power amplifiers instead of a single line amplifier (as shown in Figures 1 and 2), the overall system power can be significantly increased compared to conventional amplifiers containing a single line amplifier such as an EDFA. Because hollow-core fiber can transmit higher power optical signals (compared to solid-core fiber), it can be inferred that each optical signal can be transmitted from the corresponding transponder-amplifier at a high power level greater than 37 dBm (preferably 37 to 51 dBm). In other words, optical signals can be transmitted and transmitted at much higher power than systems using centralized amplification (as shown in Figures 1 and 2), and hollow-core fiber can handle this higher transmission power.

[0040] The preamplifiers used in the transponder-amplifier enhance the signal to match the reception of the first solid fiber network 8000A and the second solid fiber network 8000B. Optical preamplifiers are typically used to improve receiver sensitivity by pre-amplifying the signal before it reaches the first solid fiber network 8000A and the second solid fiber network 8000B. Multiple preamplifiers (in multiple transponder-amplifiers) may be identical to each other (in terms of power amplification capability) or may be different from each other.

[0041] The use of a distributed system, such as that depicted in Figure 3, results in an increase in fiber path availability of at least 40% (preferably at least 50%). In other words, if active components such as line amplifiers (see Figures 1 and 2) are eliminated from the amplifiers, reducing these amplifiers to only the multiplexers (see Figure 4), the path availability of the system becomes equivalent to the path availability of the fiber itself. With an availability of 0.995 for each device (such as the amplifier in Figure 1), the path availability changes from 94% to 97%, thereby reducing total downtime by 10% to 50%. It should be noted that, since the amplifiers are integrated into the transponders, it is preferable not to position the amplifiers downstream of the mux / demux (1000A, 1000B) and upstream of the hollow fiber network 6000.

[0042] Figure 4 is a schematic diagram of an exemplary multiplexer-demultiplexer mux / demux 1000A without active components such as the line amplifiers and preamplifiers of Figure 1. As described above, the active components are removed from the multiplexer 1000A and combined with the repeater to form the repeater-amplifier shown and described in Figure 3. Therefore, Figure 4 represents the multiplexer 1000A of Figure 3, which has no amplification capability, which has been transferred to the repeater.

[0043] Figure 4 is a schematic diagram of a mux / demux 1000A (or mux / demux 1000B) that communicates optically with hollow fiber 2000 on the transmitter side and hollow fiber 4000 on the receiver side. Both hollow fibers 2000 and 4000 communicate optically with a hollow fiber network (not shown).

[0044] The multiplexer / demultiplexer 1000A transmits data in the form of optical signals from multiple solid optical fibers (not shown) to hollow optical fiber 2000 on the transmitter side, and transmits data from hollow optical fiber 4000 to multiple solid optical fibers (not shown) on the receiver side.

[0045] The solid fiber optic network (not shown) upstream of the mux / demux 1000A typically includes routers and multiple repeater-amplifiers 5020A, 5020B, ..., 5020n, 5040A, 5040B, ..., 5040n (neither of which are shown in Figure 4). Data flows in via the routers and is fed to the repeater-amplifiers, which map the signal to WDM or DWDM wavelengths and transmit it via multiple input connectors 1020 (described in detail below) to a high-power multiplexer 1040 to combine the optical signals.

[0046] The high-power multiplexer 1040 is used to receive optical signals at a higher power level of 37 to 51 dBm. Since the mux / demux 1000A of Figure 4 receives the enhanced input optical signal from the multiple transponder-amplifiers 5020A, 5020B, ..., 5020n of Figure 3, it receives the input signal power at a higher power level than 37 dBm (preferably 37 to 51 dBm). This contrasts with the prior art amplifier 100 of Figure 1, in which the input signal power is received at a power level of 22 to 36 dBm and amplified to 37-51 dBm by the line amplifier 108 along line 105. Therefore, the input optical signal power level is increased by more than 40% (preferably more than 50%) compared to a conventional amplifier with a line amplifier.

[0047] The transmitter side of the Mux / demux 1000A includes multiple input connectors 1020 for contacting multiple solid optical fibers (not shown), which transmit data as optical signals to a multiplexer 1040. The multiplexer 1040 is located upstream of a first beam splitter 1060 that communicates optically with an optical channel monitor (OCM) 1090. The multiplexer 1040 communicates optically with the multiple input connectors 1020 and uses WDM or DWDM to select among multiple inputs received from the multiple solid optical fibers contacting the multiple input connectors 1020. The multiplexer 1040 transmits these optical signals to a first single optical fiber 1050 at a power level of 37 to 51 dBm (the same as the power level it receives) without any further amplification.

[0048] The light extracted from the first single optical fiber 1050 by the beam splitter 1060 allows the optical channel monitor 1090 to measure data about the optical transmission signal. The optical channel monitor 1090 is a multi-channel dense wavelength division multiplexing (DWDM) integrated optical component designed for use in systems with up to 40 channels. In this embodiment, the optical channel monitor 1090 is an arrayed waveguide grating (AWG) based product with the additional function of optical detection. It can use a series of integrated photodetectors that simultaneously sample each channel. This allows for real-time power measurements, enabling channels in remote point-to-point or metropolitan area rings to be equalized by a group of electronically variable optical attenuators (EVOAs). Because the optical channel monitor 1090 can monitor all DWDM channels simultaneously, it can be used as an effective optical protection device (detecting any drop in signal strength) or simply as a monitor to allow network operators to track which channels are active.

[0049] Downstream of the beam splitter is an electronically variable optical attenuator (EVOA) 1110, which ensures that each transmission along the first single fiber 1050 is identical in terms of received power. The first single fiber 1050 communicates optically with an output connector 1240, which in turn communicates with a hollow fiber 2000.

[0050] An optical time reflectometer (OTDR) 1140 communicates with the first single fiber 1050 via coupler 1100 and beam splitter 1120. The OTDR measures the backscattered light from the fiber to identify any loss or fault in the first single fiber. Downstream of the OTDR 1140 is an optical monitoring channel (OSC) 1200, which communicates with the first single fiber 1050 via optical coupler 1220. The OSC provides continuous monitoring capabilities that allow real-time monitoring of the mux / demux 1000A's performance.

[0051] On the receiver side of the mux / demux 1000A, hollow fiber 4000 contacts input connector 4020, which in turn contacts a second single fiber 4050. Downstream of input connector 4020 are beam splitters 4040 for optical communication with the OSC 1200 and optical couplers 4060 and 4100 for optical communication with the OTDR 1140. The input optical signal from hollow fiber 4000 is first filtered to remove any spurious input from amplifiers on the other transmitter side. Demultiplexer 4160 takes the input optical signal from the second single fiber 4050 and then switches it sequentially to any one of the multiple individual output lines. Demultiplexer 4160 can convert the serial optical signal received from hollow fiber 4000 into a parallel data stream, where each data stream can be directed to each of the multiple solid fibers that contact the multiple output receiver connectors 4200.

[0052] The output received at connector 4200 is then fed to a plurality of transponder-amplifiers 5020A, 5020B, ..., 5020n depicted in Figure 3, wherein distributed preamplifiers enhance the optical signal power to match the receiving first solid fiber network 8000A and second solid fiber network 8000B (see also Figure 3).

[0053] Removing amplification power from traditional optical amplifiers and redistributing that power to the multiple transponder-amplifiers detailed in this paper offers significant system advantages over traditional amplifiers. Failure of active components, such as line amplifiers or preamplifiers, will no longer render the entire network inoperable. This reduces the blast radius of a failure. Fewer customers will be affected.

[0054] Because the amplification capability is distributed, amplifier saturation is mitigated. Transmit power (the power of the optical signal) can be increased without amplifier saturation due to the use of a large number of amplifiers. Overall system power is significantly increased compared to systems where this amplification capability is centralized. This allows for increased network size—the use of distributed amplification enables larger metropolitan area ring networks. Furthermore, overall system downtime is reduced by 10% to 50% compared to systems using centralized amplification.

[0055] While the invention has been described with reference to some embodiments, those skilled in the art will understand that various changes can be made and its elements can be substituted with equivalents without departing from the scope of the invention. Furthermore, many modifications can be made to adapt particular situations or materials to the teachings of the invention without departing from the basic scope of the invention. Therefore, it is intended that the invention be limited to the specific embodiments disclosed as the best mode contemplated for carrying out the invention, but that the invention encompass all embodiments falling within the scope of the appended claims.

Claims

1. A system for transmitting optical signals between a first solid-core optical fiber network (8000A) and a hollow-core optical fiber network (6000), the system comprising: A first plurality of transponder-amplifiers (5020A, 5020B, ..., 5020n); wherein each of the plurality of transponder-amplifiers includes a transponder optically communicating with one of a power amplifier and a preamplifier; wherein the plurality of transponder-amplifiers (5020A, 5020B, ..., 5020n) optically communicates with the first solid fiber network (8000A) and is used to receive a plurality of first optical signals from the plurality of transponder-amplifiers (5020A, 5020B, ..., 5020n); and a multiplexer ( 1000A), the multiplexer (1000A) is located downstream of the plurality of transponder-amplifiers (5020A, 5020B, ..., 5020n); wherein the multiplexer (1000A) is used to receive the plurality of first optical signals; wherein the multiplexer (1000A) is used to select among the plurality of first optical signals received from the plurality of transponder-amplifiers (5020A, 5020B, ..., 5020n), and transmit at least one of the plurality of first optical signals to the hollow fiber network (8000B).

2. The system of claim 1, wherein each transponder-amplifier (5020A, 5020B, ..., 5020n) comprises both the power amplifier (5021A) and the preamplifier (5023A).

3. The system of claim 1, wherein the power amplifier (5021A) is used to amplify the input optical signal received from the solid fiber network (8000A) to a power level greater than 37 dBm.

4. The system of claim 1, wherein the preamplifier (5023A) is used to enhance the optical signal before transmitting the optical signal received from the hollow fiber network (8000A) to the solid fiber network (8000B).

5. The system of claim 4 further includes a demultiplexer (1000B) located upstream of the second plurality of transponder-amplifiers (5040A, 5040B, ..., 5040n); wherein the demultiplexer (1000B) is used to demultiplex the at least one optical signal received from the hollow fiber network (6000) and transmit the at least one optical signal to the preamplifier (5043A) included in the second plurality of transponder-amplifiers (5040A, 5040B, ..., 5040n).

6. The system of claim 5, wherein the multiplexer (1000A) and demultiplexer (1000B) do not have amplifiers and preamplifiers.

7. The system of claim 5, wherein the demultiplexer (1000B) is used to transmit the optical signal to one of a plurality of preamplifiers (5043A, 5043B, ..., 5043n) included in the plurality of transponder-amplifiers (5040A, 5040B, ..., 5040n).

8. The system of claim 1, wherein each of the plurality of transponder-amplifiers (5020A, 5020B, ..., 5020n) operates independently of each other.

9. The system of claim 5, wherein the multiplexer (1000A) further comprises one of the following: an optical domain time reflectometer (1040), an optical monitoring channel (1200), and an optical channel monitor (1090).

10. The system of claim 1, wherein at least one power amplifier (5021A) of the plurality of transponder-amplifiers (5020A, 5020B, ..., 5020n) is different from another power amplifier (5021B) of the plurality of transponder-amplifiers.

11. The system of claim 1, wherein at least one power amplifier among the plurality of transponder-amplifiers (5020A, 5020B, ..., 5020n) is used to amplify the optical signal to a power level of 37 to 51 dBm.

12. The system of claim 1, wherein the system downtime is reduced by at least 10% to 50% compared to the comparative system, wherein the multiplexer (1000A) in the comparative system comprises a line amplifier.

13. A method for transmitting optical signals between a solid-core optical fiber network (8000A) and a hollow-core optical fiber network (6000), comprising: A plurality of first optical signals are transmitted from the solid-core fiber network (8000A) to a plurality of transponder-amplifiers (5020A, 5020B, ..., 5020n); wherein each of the plurality of transponder-amplifiers (5020A, 5020B, ..., 5020n) includes a transponder in optical communication with a power amplifier and a preamplifier; the plurality of first optical signals are amplified using the power amplifiers (5021A, 5021B, ..., 5021n); a multiplexer (1000A) located downstream of the plurality of transponder-amplifiers (5020A, 5020B, ..., 5020n) is used to select among the plurality of first optical signals received from the plurality of transponder-amplifiers (5020A, 5020B, ..., 5020n); and at least one optical signal from the plurality of first optical signals is transmitted to the hollow-core fiber network (6000).

14. The method of claim 13, further comprising: The second plurality of optical signals received from the hollow fiber network (6000) are demultiplexed, and at least one optical signal from the plurality of second optical signals is transmitted to the preamplifier; The demultiplexer (1000B) is located upstream of the plurality of transponder-amplifiers (5040A, 5040B, ..., 5040n).

15. The method of claim 13, wherein no further amplification of the at least one optical signal is performed after the multiplexing.

16. The method of claim 13, further comprising: Each of the plurality of transponder-amplifiers (5020A, 5020B, ..., 5020n) operates independently of the others.

17. The method of claim 14, further comprising: The second optical signal is amplified before being transmitted to the solid fiber network via the preamplifiers (5043A, 5043B, ..., 5043n).

18. The method of claim 13, further comprising: The power amplifier is used to amplify the first optical signal to a power level greater than 37 dBm.

19. The method of claim 18, further comprising: The first optical signal is amplified to a power level of 37 to 51 dBm.

20. The method of claim 13, further comprising: A first optical signal from the plurality of first optical signals is amplified in a first transponder-amplifier (5020A) among a plurality of transponder-amplifiers (5020A, 5020B, ..., 5020n), and a second optical signal from the plurality of first optical signals is amplified in a second transponder-amplifier (5020B) among a plurality of transponder-amplifiers (5020A, 5020B, ..., 5020n); wherein the amplification of the first optical signal and the amplification of the second optical signal are performed differently.

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