Experimental characterization of a 400  Gbit/s orbital angular momentum multiplexed free-space optical link over 120 m

Abstract

Ren, Y. et al. (2016) Experimental characterization of a 400 Gbit/s orbital angular momentum multiplexed free-space optical link over 120 m. Optics Letters, 41(3), pp. 622-625.There may be differences between this version and the published version. You are advised to consult the publisher's version if you wish to cite from it.http://eprints.gla.ac.uk/115873/ Free-space optical (FSO) communications has attracted much attention for a variety of applications, such as back-haul and data centers [1, 2]. Given the rapid growth of bandwidth demand for these applications, there is increased interest in utilizing advanced multiplexing of multiple data streams to increase the data capacity and spectral efficiency of an FSO system [3]. Multiplexing in wavelength and polarization, known as wavelength division multiplexing (WDM) and polarization division multiplexing (PDM) respectively, have previously been used for FSO transmission [3, 4]. Another potential approach is to use space division multiplexing (SDM), for which multiple beams each carrying an independent data stream are transmitted through a common medium [5, 6]. Provided these spatially-overlapping beams can be properly demultiplexed with tolerable crosstalk, the total capacity and spectral efficiency of the communication system is increased by a factor equal to the number of transmitted orthogonal modes. An orthogonal spatial modal basis set for SDM that has gained interest is orbital angular momentum (OAM) [5][6][7][8]. OAM beams with different ℓ values (ℓ is an unbounded integer) are mutually orthogonal [8, 9], so that beams carrying different OAM can act as independent data channels for efficiently multiplexing multiple information-bearing signals in an SDM-based communication system [5]. Moreover, similar to any SDM approach, OAM multiplexing is in principle compatible with existing WDM and PDM techniques [6]. We note that compared to other modal sets, such as Hermite-Gaussian (HG) modes that could also be used for SDM, OAM modes might offer the potential advantage of being conveniently matched to many optical subsystems due to their circular symmetry.It is known that the amount of phase change per unit area for an OAM beam is greatest in the beam center, and that collecting sufficient phase changes is critical for ensuring orthogonality among OAM beams [9]. As a result, OAM multiplexing might be more sensitive to system alignment as it relies more critically on a common optical axis to achieve low inter-modal crosstalk [10]. OAM multiplexing has been employed to demonstrate high-capacity FSO transmission links in laboratory settings [6, 7]. These experiments were generally

Orbital Angular Momentum Waves: Generation, Detection, and Emerging Applications

“…In a similar fashion, in [102] a transmission rate of 1.036 Pbps with a spectral efficiency of 112.6 bps/Hz has been achieved by multiplexing 54.139 Gbps OFDM-8QAM signals over 368 wavelengths, 2 polarization states and 26 OAM modes. In addition to these lab-scale high-rate data experiments, a 400 Gbps transmission rate has been achieved over an outdoor link of about 120m by using 100 Gbps QPSK signals on 4 OAM modes [103].…”

Recent advances in high-capacity free-space optical and radio-frequency communications using orbital angular momentum multiplexing

“…Ren et al [40] reported a 400 Gbit s −1 data link over 120 m by multiplexing four OAM beams with = −3, −1, +1 and +3. As shown in figure 7, the transmitter and receiver were located at the same site on the roof of (d) Link parameter design for orbital angular momentum-based free-space optical systems…”

Integrated optical modulator manipulating the polarization and rotation handedness of Orbital Angular Momentum states

“…In the integrated optical devices, phase, amplitude, and polarization of the electric field of the optical communication signal are modulated using miniaturized waveguides with straight or interferometric configurations 21 . As it is mentioned above, one of the possible approaches to increase the capacity of an optical 7, 22–24 or quantum 9 channel is the using of an optical signal carrying OAM . Although integrated optically generation, detection, multiplexing, and switch of the optical signals with different OAM values are demonstrated 25–32 , but neither modulators nor switches for manipulating a specific guided mode carrying OAM integrated optically have been proposed.…”