The present invention generally relates to fiber optic communication systems, and more particularly relates to a low-latency fiber based communication system that utilizes hollow core fiber.
Conventional fiber optic communications systems are widely employed to transfer data between remote locations. Conventional fiber optic cable typically includes a solid core single mode fiber (SMF) having a solid core material and a solid cladding surrounding the core. In conventional single mode fiber, the solid core is composed of glass and has a refractive index of about 1.45 to 1.48 depending on the level of doping and wavelength. Light travels in the solid core generally at a reduced speed as compared to light transmission in air or a vacuum, e.g., about 1.45 times slower than the speed of light in a vacuum. In a communication system, latency is the temporal delay experienced by a packet of information traveling from the transmitter to the receiver. The total latency is determined by propagation speed, packet size, routing, optical and electrical compensation of errors and impairments, storage delays and other optical and electrical delays in the system.
In more recent years, hollow core fiber which is based on the physics of photonic band-gaps has been developed and is generally also referred to as photonic band-gap fiber (PBGF). The hollow core fiber typically has a hollow core surrounded by a silica cladding containing a multitude of continuous air holes that form a periodic lattice structure. An alternative hollow core design uses high-index rods to form a photonic band-gap lattice in a glass matrix surrounding a hollow core. The hollow core fiber allows light to be guided in a low-index medium such as a gas, a mixture of gases or a vacuum, such that the group refractive index is slightly greater than unity and light velocity is typically around 0.9975 to 0.95 times the speed of light in a vacuum. Hollow core fiber typically results in reduced-latency, however, conventional hollow core fibers typically have higher losses and therefore require more optical power to be launched at the transmitter or at optical amplification points.
The need for lower-latency and reduced loss fiber optic based communication systems has arisen in several markets. For example, the financial trading markets are in need of a communication systems that allow decreased data transmissions times between trading computers. This will enable trading programs to complete programmed trading transactions more quickly. Accordingly, there is a need to provide low-latency fiber optic based communication to meet the needs of low-latency applications.
According to one embodiment, an optical fiber communication system is provided. The optical fiber communication system includes a transmitter device and a receiver device. The communication system also includes a hollow core fiber optically coupled to the transmitter device, wherein less than ten percent (10%) of the total length of solid core fiber in a span exists between the transmitter device and the hollow core fiber. The communication system further includes a solid core fiber operatively coupled between the hollow core fiber and the receiver device.
According to another embodiment, an optical fiber communication system is provided that includes a transmitter device, a receiver device and a hollow core fiber comprising a multi-mode portion of a length greater than 20 kilometers.
According to a further embodiment, an optical fiber communication system is provided that includes a transmitter device and a receiver device. The optical fiber communication system also includes a hollow core transmission fiber in optical communication with the transmitter device, and a solid core transmission fiber operatively coupled to the hollow core fiber. The communication system further includes a Raman pump laser coupled to the solid core transmission fiber for providing distributed Raman amplification in the solid core transmission fiber.
According to yet a further embodiment, an optical fiber communication system is provided that includes a transmitter device, a receiver device, and a plurality of serially connected spans. Each span includes a hollow core fiber and a solid core fiber operatively coupled to the hollow core fiber.
According to a further embodiment, a communication system is provided that includes a first transceiver, a second transceiver and a cable. The communication system also includes a first transmission line in the cable and operatively coupled between the first transceiver and the second transceiver. The communication system further includes a second transmission line in the cable and coupled between the second transceiver and the first transceiver. Each of the first and second transmission lines comprises a hollow core fiber.
Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described herein, including the detailed description which follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description are merely exemplary, and are intended to provide an overview or framework to understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate one or more embodiments, and together with the description serve to explain principles and operation of the various embodiments.
Reference will now be made in detail to the present preferred embodiments, examples of which are illustrated in the accompanying drawings. Whenever possible, the same reference numerals will be used throughout the drawings to refer to the same or like parts.
Various embodiments of an optical fiber communication system exhibiting low-latency, low-loss, and low-nonlinear penalties are provided that include a hollow core fiber coupled between a transmitter device and a receiver device. A hollow core fiber is defined as a fiber having a hollow core which provides a photonic band-gap and is also referred to herein as a photonic band-gap fiber. The hollow core has a low index medium which may include a gas, a mixture of gases, or a vacuum. In one embodiment, the hollow core is surrounded by a silica cladding containing a multitude of continuous air holes that form a periodic lattice structure as shown in
The communication system may also employ a solid core fiber connected in combination with the hollow core fiber between the transmitter device and the receiver device to form a hybrid fiber transmission path. The solid core fiber is defined as a fiber having a solid core made of a solid material, such as glass, that has a refractive index that is higher than the refractive index of the hollow core fiber. The solid core fiber may include single mode fiber. The total length of solid core fiber is the sum of all of the lengths of solid core fiber in a span between the transmitter device and the receiver device. In some embodiments, less than ten percent (10%) of the total length of solid core fiber in the span is present between the transmitter device and the first hollow core fiber. According to one embodiment, less than five percent (5%) of the total length of solid core fiber in the span is present between the transmitter device and the first hollow core fiber. According to a further embodiment, less than one percent (1%) of the total length of solid core fiber in the span is present between the transmitter device and the first hollow core fiber. According to yet another embodiment, zero percent (0%) or no solid core fiber is present between the transmitter device and the first hollow core fiber.
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The communication system 10 shown in
The hollow core fiber 16 may include a multi-mode fiber having a length greater than 20 kilometers, according to one embodiment. According to another embodiment, the hollow core multi-mode fiber has a length greater than 100 kilometers. According to one embodiment, the hollow core fiber 16 may include a single mode fiber. The solid core fiber 20 may include a single mode fiber, according to one embodiment. The solid core fiber 20 has a significant length such as 20 km to 50 km, according to one embodiment. While a single span of series connected hollow core fiber 16 and solid core fiber 20 is shown providing a single span in this embodiment, it should be appreciated that multiple series connected spans of hollow core fiber 16 and solid core fiber 20 may be employed between the transmitter device 12 and receiver device 22.
While the optical fiber communication system 10 is shown having a hollow core fiber 16 and a solid core fiber 20, according to one embodiment, it should be appreciated that the optical fiber communication system 10 may employ a hollow core fiber 16 absent any significant length of solid core fiber. In one embodiment, the optical fiber communication system may include a hollow core fiber 16 including a multi-mode portion of a length greater than 20 kilometers disposed between the transmitter device 12 and receiver device 22. According to another embodiment, the multi-mode portion of the hollow core fiber 16 may have a length greater than 100 kilometers. It should be appreciated that a solid core fiber may be coupled to the hollow core fiber and that the solid core fiber may be a single mode fiber, according to one embodiment.
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The hollow core fiber 16 preferably is the first fiber in a given span such that it precedes the solid core fiber 20 in a direction of data communication. The hollow core fiber 20 generally has no or little non-linearities, but exhibits higher losses as compared to the solid core fiber and therefore requires more power. By employing a multi-mode hollow core fiber, optical signal transmission is realized at a reduced signal loss due to the reduced attenuation. For long distance transmissions, a high launch power may be employed which may be achieved with the erbium doped fiber amplifier 14. In addition, the Raman distributed amplification provides additional power for the transmission over a long distance. It should be appreciated that a higher proportion of hollow core fiber 16 will result in a lower-latency, but will require more power to make up for the attenuation losses.
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The various embodiments as shown in
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The hollow core fiber preferably precedes the solid core fiber in some embodiments since it has substantially zero non-linear impairment and thus can be used with high launch powers. By the time the optical signal reaches the solid core fiber, the hollow core fiber attenuation may have decreased the power to a point where further non-linear impairment should be very small. Although the latency of the transmission will be increased due to the solid core fiber, the total span attenuation will be significantly reduced with the hybrid hollow core fiber and solid core fiber embodiments. According to one example, a span having 40 kilometers of hollow core fiber may have an attenuation drop of about 40 dB, whereas a hybrid span having 50% half hollow core and 50% half solid core fibers may achieve an attenuation drop of about 24 dB. The average latency will be improved while achieving a more controlled attenuation drop by employing the hybrid fiber communication system 10.
It should be appreciated that the proportion of hollow core fiber to solid core fiber may vary depending upon the desired latency and acceptable losses, desired bit rate and bit error rate. In one embodiment, each span employs equal lengths of hollow core fiber and solid core fiber. According to other embodiments, a greater distance of hollow core fiber allows for a greater reduction in latency. It should further be appreciated that launch power required to maintain the signal strength may vary depending upon the length of the transmission and the amount of hollow core fiber as compared to solid core fiber. The launch power required can be calculated based on known characteristics of the fibers employed and the length of transmission paths.
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The optical fiber communication system 10 or 100 may be employed to communicate data between first and second computers. According to one embodiment, the communication system 10 or 100 may interconnect computers that are used for financial transactions, particularly those that extend a long distance from one city to another. It should be appreciated that the communication system 10 or 100 may be employed in other applications to transmit optical signals between remote locations. The communication system 10 or 100 advantageously reduces the transmission time to transmit data between the transmitter and receiver devices with a managed signal low and without exceptional non-linear penalties to achieve a low-latency communication system. The communication system 10 and 100 advantageously overcomes high attenuation problems associated with the hollow core fiber, according to various embodiments.
It will be apparent to those skilled in the art that various modifications and variations can be made without departing from the spirit or scope of the claims.