All-optical Link Research Articles

Interconnected Transparent Island Architectures for Low-Latency Hyperscale Datacenters

In this letter, we propose a novel hyperscale datacenter network architecture named Interconnected Transparent Island (ITI). The ITI architecture efficiently interconnects several transparent islands with each other. Each island consists of full-mesh transparent rings connecting all pods through single hop all-optical links. The proposed architecture offers high scalability, fewer overall hops and lower power consumption with the ability to connect over one Million servers. We have compared our proposed architecture with Facebook F16 fabric aggregator topology. Results from theoretical analysis and simulations show that ITI is a viable topology for large-scale datacenter networks.

Integrated system of free‐space optical and visible light communication for indoor wireless broadband access

An integrated system of free-space optical communication and visible light communication for indoor wireless broadband access is proposed. The proposed system features all-optical links and high capacity. As a proof of concept, 16- and 32-quadrature amplitude modulation single-carrier frequency domain equalisation transmissions over equivalent 2 km free-space, 1 km single-mode fibre, and 2 m indoor free-space link are demonstrated. About 300 Mbit/s data rate with bit error rate under the forward error correction limit (3.8 × 10−3) and clear constellation maps are achieved.

Performance Analysis of Relay-Assisted All-Optical FSO Networks Over Strong Atmospheric Turbulence Channels With Pointing Errors

In this study, we consider a relay-assisted free-space optical communication scheme over strong atmospheric turbulence channels with misalignment-induced pointing errors. The links from the source to the destination are assumed to be all-optical links. Assuming a variable gain relay with amplify-and-forward protocol, the electrical signal at the source is forwarded to the destination with the help of this relay through all-optical links. More specifically, we first present a cumulative density function (CDF) analysis for the end-to-end signal-to-noise ratio. Based on this CDF, the outage probability, bit-error rate, and average capacity of our proposed system are derived. Results show that the system diversity order is related to the minimum value of the channel parameters.

All-optical link for direct comparison of distant optical clocks

We developed an all-optical link system for making remote comparisons of two distant ultra-stable optical clocks. An optical carrier transfer system based on a fiber interferometer was employed to compensate the phase noise accumulated during the propagation through a fiber link. Transfer stabilities of 2 × 10(-15) at 1 second and 4 × 10(-18) at 1000 seconds were achieved in a 90-km link. An active polarization control system was additionally introduced to maintain the transmitted light in an adequate polarization, and consequently, a stable and reliable comparison was accomplished. The instabilities of the all-optical link system, including those of the erbium doped fiber amplifiers (EDFAs) which are free from phase-noise compensation, were below 2 × 10(-15) at 1 second and 7 × 10(-17) at 1000 seconds. The system was available for the direct comparison of two distant (87)Sr lattice clocks via an urban fiber link of 60 km. This technique will be essential for the measuring the reproducibility of optical frequency standards.

Transmission of active and passive optical reference signals over a 16 channel, 534.4 km WDM optical fibre network

Active and passive optical frequency reference signals have been transmitted over a 534.4 km optical fibre network carrying live traffic and an equivalent fibre test-bed. The active references comprised an optical-transition locked fibre-laser and a fibre-grating locked distributed feedback (DFB) laser. A low-finesse etalon and molecular absorptions in an acetylene gas cell were used as passive references. No degradation of the reference wavelength was observed down to the 10 -8 level and in a self-heterodyne experiment; the upper limits for line-broadening and frequency shift of the transmitted signal are 2 x 10 -9 , limited by the DFB characteristics. Amplified spontaneous emission (ASE) noise and interference signals were observed for active references. The passive reference signals were also degraded by the ASE noise. The technical and logistical issues associated with using a long-distance point-to-point all-optical link for frequency metrology have been discussed.

US phone companies set stage for fiber to the curb

From almost the dawn of the Internet, phone and cable companies have been fighting for the hearts and minds of the savvier consumers all over the world. The key battleground is the so-called last-mile link to the home or business, where the phone companies have been pitting their digital subscriber lines (DSLs) against the cable providers' cable modems. In most places in the world, DSLs have been the more popular option, though in the United States, with its very large cable infrastructure, cable modems have had a distinct edge. All along, however, the Holy Grail has been fiber to the curb-an all-optical link going right into homes or businesses and providing bandwidth and speed that just can't be beat. Now, three of the four US regional Bell operating companies (RBOCs, or Baby Bells)-Verizon, BellSouth, and SBC-intend to start building such fiber-optic networks to the premises as early as the first quarter of 2004. Verizon Communications has by far the most ambitious plans: it says it intends to provide every home and business it serves with a fiber-optic connection during the next 10-15 years, at an estimated total cost of as much as US $40 billion. Verizon, BellSouth, and SBC got together and agreed on a common set of specifications for fiber to the curb. They are considering responses from vendors to their requests for proposed equipment built to those specs.

Transparent supervision of optically amplified fibre links with received signal and ASE monitoring

This paper illustrates that remote fault localisation in all-optical links with concatenated fibre amplifiers can be performed by simple monitoring of the signal and the accumulated ASE noise powers at the receiver end. The method is first presented in ideal operating conditions, and second, the effect of the spontaneous emission factor variation and the EDFA non-linear behaviour are taken into account. From the analysis, the requirements of the link design for proper supervision accuracy are derived. The presented supervisory method is a simple solution for links where a fibre break or an amplifier fault is to be detected and located with the granularity of an amplifier section without local supervisory elements within the transmission sections.

Optical vibrating quartz crystal pressure sensor using frustrated-total-internal-reflection readout technique

An optically driven, through photovoltaic conversion, pressure sensor is described which uses frustrated-total-internal-reflection between a critically cut optical fiber and a quartz crystal, mounted on a cantilever beam to sense the device resonant frequency. The change in this frequency as a function of applied pressure is measured in this sensor which relies upon an all-optical link to the control electronics.