We demonstrated low cost and power-efficient a 2.5 Gb/s optical wireless transmission system at 10 cm distance, which should be employed in high-energy physics experiments such as Compact Muon Solenoid. The system uses an off-the-shelf VCSEL and a PIN photodiode with proper ball lens. Its most attractive feature is that it does not need a complex active tracking system because its measured tolerance to misalignment is around +/-1mm at Bit Error Rate of 10^-12. The experimental results show that this can be a viable solution for future HEP experiments.

Simplified coherent detection of directly-modulated DFB transmitters allows for 55 dB ODN power budget in downstream of a 40 Gb/s DML-based WDM-PON with 110 km reach. The solution can enhance NGPON2, addressing long reach and high power budget links (>50 dB).

We demonstrate experimentally a novel type of coherent low cost Gigabit-to-the-User Ultra-Dense-Wavelength Division Multiplexing (UD-WDM) PON, featuring 6.25 GHz channel spacing and long reach.Polarization-independent coherent detection is achieved by exploiting a novel scheme which requires only a 3 × 3 coupler, three photodiodes, basic analogue processing and a common DFB as local oscillator (LO).This avoids the conventional polarization diversity approach.The DFB LO is free running, i.e. not locked in frequency, and is tuned to detect any of the eight channels by simply changing its temperature in a range of 2 °C.We achieve 70 km long-reach transmission plus 30 dB attenuation, for a total of > 45 dB optical distribution network loss.This indicates that this solution could be effectively exploited to overlay existing PON infrastructures by UD-WDM.

Processing of high-frequency, wide-band signals is conveniently performed in the optical domain due to availability of optical filters which intrinsically have a wide-band response. On the other end, there are several application scenarios where very sharp pass-band filtering is required. In these cases, realizing the processing in the optical domain might not be technically simple, although filters of extremely high Q-factor have been demonstrated. This paper presents the feasibility of signal processing based on very sharp electrical filtering (< 1 GHz around 193 THz) assisted by optical down-conversion, i.e., by means of optical coherent detection. In particular, we show experimentally two applications where the filtering capability is exploited to perform signal processing: the demodulation of phase-modulated optical signals and the implementation of a chirp-managed transmission link. Other possible applications of this technique will be also discussed at the presentation.

High speed optical fiber or copper wire communication systems are frequently deployed for readout data links used in particle physics detectors. Future detector upgrades will need more bandwidth for data transfer, but routing requirements for new cables or optical fiber will be challenging due to space limitations. Optical wireless communication (OWC) can provide high bandwidth connectivity with an advantage of reduced material budget and complexity of cable installation and management. In a collaborative effort, Scuola Superiore Sant' Anna and INFN Pisa are pursuing the development of a free-space optical link that could be installed in a future particle physics detector or upgrade. We describe initial studies of an OWC link using the inner tracker of the Compact Muon Solenoid (CMS) detector as a reference architecture. The results of two experiments are described: the first to verify that the laser source transmission wavelength of 1550 nm will not introduce fake signals in silicon strip sensors while the second was to study the source beam diameter and its tolerance to misalignment. For data rates of 2.5 Gb/s and 10 Gb/s over a 10 cm working distance it was observed that a tolerance limit of +/- 0.25 mm to +/- 0.8 mm can be obtained for misaligned systems with source beam diameters of 0.38 mm to 3.5 mm, respectively.

A new laser suitable for access-systems with FM efficiency up to 7 GHz/mA and negligible amplitude modulation is presented. It enables 1.25/2.5 Gb/s operations with extremely low driving signals: 70 mVpk-pk and 250 mVpk-pk respectively.

Optical Wireless Communication (OWC) system for particles detector can be a viable solution for reducing the complexity of the optical fibre network used to extract the data from the detector. In this work we present the initial study of the tolerance to misalignment for the OWC system under investigation. We observed that using collimators of beam waist from 0.35mm to 3.5mm we can obtain tolerance in range from ±0.25mm to ±0.8mm. We also observed using ray trace simulation that both transmitting power and tolerance can be improved by using optimized lens at the receiver having VCSEL as transmitting source.

This paper presents the implementations and test results of the novel polarization-independent receiver for ASK format, realized in the framework of COCONUT FP7 Project. COCONUT exploits low-cost optical components and simple electronics, so that the cost of typical line terminals would be affordable to the end-users. Among the different technical approaches considered within the project; we focus here on the solutions based on simple OOK-NRZ format. We developed an original improvement of the conventional phase-diversity coherent detection schemes, providing for polarization independent operations without doubling the receiver structure. As a result we demonstrated that polarization-independent coherent detection is feasible within the constraint of limited cost typical of passive access networks. The developed receivers can allow for high-power budget (> 45 dB and ultra-dense WDM operation (6.25 GHz grid).

We experimentally demonstrate a cost-effective coherent 10 Gb/s system for passive optical networks, exploiting off-the-shelf DFB lasers and a phase-diversity receiver based on a simple 3 × 3 fiber coupler. Since the system uses a simple amplitude-shift keying format, no complex electronic processing is required and there is no need of frequency/phase stabilization of the local oscillator, whose frequency can change by more than ±1 GHz with no significant performance variation. The system has a 40 dB loss budget and is, therefore, compatible with the high losses of practical optical distribution networks, where power splitting is used to distribute the signal to a high number of users. Error-free 10-Gb/s transmission at the FEC limit is obtained after transmission over up to 66 km of G.652 single mode fiber. Polarization-independent operation is also demonstrated with a simple modification of the detection scheme, without duplicating components, and with a small variation of the sensitivity. The limited complexity indicates the potential for a cost-effective implementation, which makes it compatible with the strictly cost-aware access networks environment, even for high-end services.

In this paper we experimentally realized bidirectional optical wireless communication (OWC) link using four channel visible LED board exploiting wavelength division multiplexing (WDM) for the downlink and infrared LED for uplink. We achieved greater than 5 Gbit/s data rate at common indoor distance (1.5 to 4 m) for downlink and 1.5 Gbit/s for uplink using commercially available LEDs. We achieved these results after a careful choice of the LED emission wavelengths and the optical filter spectra. Moreover, we investigate the optimal LED working current and the optimal modulation depth. The bit error ratios of all the channels were maintained lower than the FEC limit (3.8·10(-3)).

In this paper we experimentally realized bidirectional optical wireless communication (OWC) link using four channel visible LED board exploiting wavelength division multiplexing (WDM) for the downlink and infrared LED for uplink. We achieved greater than 5 Gbit/s data rate at common indoor distance (1.5 to 4 m) for downlink and 1.5 Gbit/s for uplink using commercially available LEDs. We achieved these results after a careful choice of the LED emission wavelengths and the optical filter spectra. Moreover, we investigate the optimal LED working current and the optimal modulation depth. The bit error ratios of all the channels were maintained lower than the FEC limit (3.8·10(-3)).

This paper presents the most significant results achieved in the last two years by our group in coherent ultra-dense-WDM PON for lambda-to-the-user access. Here we mostly focus on the architectures based on simple OOK-NRZ modulation format. We demonstrated the real-time implementation of our coherent receiver and we proved its compatibility with direct modulated laser (DML). Receiver sensitivities as low as -48 dBm at BER=1.10-3 for 1.25 Gb/s has been observed, showing the feasibility of a coherent ONU receiver based on devices commonly available and with limited cost. The system support quite high ODN losses and allows the lambda-to-the-user approach.

We demonstrate 10-Gb/s transmission over more than 130 km of G.652 fiber using a simple directly modulated distributed feedback (DFB) laser and a new “chirp-managed” approach based on a low-complexity coherent receiver. The “chirp-managed” effect, which has been obtained in the past by optical spectral reshaping, is conveniently achieved here by means of simple electrical filtering of the received signal at the intermediate frequency. Due to coherent detection, the receiver sensitivity was -38 dBm at bit error rate (BER) 1/4 1.8 χ 10-3. No colored filters and no dispersion compensation (optical or digital signal processing (DSP)-based) were used at the receiver side. We show that the coherent system presented here, based on off-the-shelf components, is robust against variations of DFB chirp, local oscillator detuning, and electrical filter bandwidth over ranges wide enough to guarantee a simple and cost-effective implementation for 10-Gb/s long-reach passive optical network applications.

We experimentally demostrate a 6.25 GHz grid WDM-PON based on commercially available directly-modulated DFB transmitters driven with a 650mV(pp) and simplified coherent receivers. The system can support 35dB distribution network losses and allows the lambda-to-the-user approach.

We experimentally demonstrate a 400 Mbit/s bi-directional optical wireless transmission operating in non-directed line-of-sight configuration, based on visible/infrared LEDs for downlink/uplink, exploiting adaptive Discrete Multi-Tone technique and optimized optical filters.

We experimentally rea environment distances and illum achieved exploiting WDM

We demonstrate a coherent OFDM-PON based on a simplified coherent receiver, which exploits a DFB local oscillator without phase/frequency locking. We achieve ultra-narrow channel spacing (Δν = 1.6 GHz) and high-power budget (43 dB/35 dB) for 1.25/10 Gb/s.

This paper presents the first experimental achievements of the COCONUT project which aims at demonstrating ultra-dense Wavelength Division Multiplexing Passive Optical Networks (udWDM-PON) by means of low-cost coherent solutions. COCONUT should exploit low-cost optical components and simple electronics so that the cost of typical line terminals would be affordable to the end-users. Among different technical approaches considered within the project; we focus here on the solutions based on simple OOK-NRZ format. We developed an original improvement of the conventional phase-diversity coherent detection schemes providing for polarization independent operations without doubling the receiver structure. As a result we demonstrated that passive networks of high-power budget (> 45 dB i.e. up to 60 km reach and more than 64-way power splitting) are feasible over a 6.25 GHz grid by using a limited number of photodiodes a simplified analog processing and free-running DFBs.

131 km transmission (typical LR-PON distance) at 10Gb/s over G.652 fiber is demonstrated exploiting a direct modulated (DM) DFB laser, coherent receiver and electrical filtering obtaining an innovative chirp managed approach. No dispersion compensation (optical or DSP) is exploited.