5 research outputs found
Towards a Scaleable 5G Fronthaul: Analog Radio-over-Fiber and Space Division Multiplexing
The introduction of millimeter wave (mm-wave) frequency bands for cellular communications with significantly larger bandwidths compared to their sub-6GHz counterparts, the resulting densification of network deployments and the introduction of antenna arrays with beamforming result in major increases in fronthaul capacity required for 5G networks. As a result, a radical re-design of the radio access network is required since traditional fronthaul technologies are not scaleable. In this article the use of analog radio over fiber (ARoF) is proposed and demonstrated as a viable alternative which, combined with space division multiplexing in the optical distribution network as well as photonic integration of the required transceivers, shows a path to a scaleable fronthaul solution for 5G. The trade-off between digitized and analog fronthaul is discussed and the ARoF architecture proposed by blueSPACE is introduced. Two options for the generation of ARoF two-tone signals for mm-wave generation via optical heterodyning are discussed in detail, including designs for the implementation in photonic integrated circuits as well as measurements of their phase noise performance. The proposed photonic integrated circuit designs include the use of both InP and SiN platforms for ARoF signal generation and optical beamforming respectively, proposing a joint design that allows for true multi-beam transmission from a single antenna array. Phase noise measurements based on laboratory implementations of ARoF generation based on a Mach-Zehnder modulator with suppressed carrier and with an optical phase-locked loop are presented and the suitability of these transmitters is evaluated though phase noise simulations. Finally, the viability of the proposed ARoF fronthaul architecture for the transport of high-bandwidth mm-wave 5G signals is proven with the successful implementation of a real-time transmission link based on an ARoF baseband unit with full real-time processing of extended 5G new radio signals with 800MHz bandwidth, achieving transmission over 10km of 7-core single-mode multi-core fiber and 9m mm-wave wireless at 25.5GHz with bit error rates below the limit for a 7% overhead hard decision forward error correction
5G mm wave networks leveraging enhanced fiber-wireless convergence for high-density environments:the 5G-PHOS approach
\u3cp\u3eAnalog optical fronthaul for 5G network architectures is currently being promoted as a bandwidth- and energy-efficient technology that can sustain the data-rate, latency and energy requirements of the emerging 5G era. This paper presents 5G-PHOS project approach, which relies on a new optical fronthaul architecture that can effectively synergize optical transceiver, optical add/drop multiplexer and optical beamforming integrated photonics towards a DSP-assisted analog fronthaul, administered by means of a Medium Transparent Dynamic Bandwidth Allocation (MT-DBA) protocol for seamless and medium-transparent 5G small-cell networks.\u3c/p\u3
Subwavelength grating enabled on-chip ultra-compact optical true time delay line
An optical true time delay line (OTTDL) is a basic photonic building block that enables many microwave photonic and optical processing operations. The conventional design for an integrated OTTDL that is based on spatial diversity uses a length-variable waveguide array to create the optical time delays, which can introduce complexities in the integrated circuit design. Here we report the first ever demonstration of an integrated index-variable OTTDL that exploits spatial diversity in an equal length waveguide array. The approach uses subwavelength grating waveguides in silicon-on-insulator (SOI), which enables the realization of OTTDLs having a simple geometry and that occupy a compact chip area. Moreover, compared to conventional wavelength-variable delay lines with a few THz operation bandwidth, our index-variable OTTDL has an extremely broad operation bandwidth practically exceeding several tens of THz, which supports operation for various input optical signals with broad ranges of central wavelength and bandwidth
Sub-hertz fundamental linewidth photonic integrated Brillouin laser
Photonic systems and technologies traditionally relegated to table-top
experiments are poised to make the leap from the laboratory to real-world
applications through integration. Stimulated Brillouin scattering (SBS) lasers,
through their unique linewidth narrowing properties, are an ideal candidate to
create highly-coherent waveguide integrated sources. In particular,
cascaded-order Brillouin lasers show promise for multi-line emission, low-noise
microwave generation and other optical comb applications. Photonic integration
of these lasers can dramatically improve their stability to environmental and
mechanical disturbances, simplify their packaging, and lower cost. While
single-order silicon and cascade-order chalcogenide waveguide SBS lasers have
been demonstrated, these lasers produce modest emission linewidths of 10-100
kHz. We report the first demonstration of a sub-Hz (~0.7 Hz) fundamental
linewidth photonic-integrated Brillouin cascaded-order laser, representing a
significant advancement in the state-of-the-art in integrated waveguide SBS
lasers. This laser is comprised of a bus-ring resonator fabricated using an
ultra-low loss Si3N4 waveguide platform. To achieve a sub-Hz linewidth, we
leverage a high-Q, large mode volume, single polarization mode resonator that
produces photon generated acoustic waves without phonon guiding. This approach
greatly relaxes phase matching conditions between polarization modes, and
optical and acoustic modes. Using a theory for cascaded-order Brillouin laser
dynamics, we determine the fundamental emission linewidth of the first Stokes
order by measuring the beat-note linewidth between and the relative powers of
the first and third Stokes orders. Extension to the visible and near-IR
wavebands is possible due to the low optical loss from 405 nm to 2350 nm,
paving the way to photonic-integrated sub-Hz lasers for visible-light
applications