Hybrid WDM FSO Fiber Access Network With Rayleigh Backscattering Noise Mitigation

Abstract

In the paper, we present and investigate an integrated wavelength-division-multiplexing (WDM) free space optical (FSO) fiber access network for 51 km long-reach connection. Here, the proposed network architecture also can mitigate Rayleigh backscattering (RB) interferometric beat noise. We employ symmetric 4 × 10 Gbit/s on-off keying (OOK) WDM-FSO downstream and upstream wavelengths for demonstration. According to the simulated and experimental results, the free space transmission length of 400 to 940 m can be achieved based on various WDM-FSO downstream signals and their corresponding power budget, when the wavelengths are without optical amplification. INDEX TERMS Free space optical (FSO) communication, passive optical network (PON), wavelengthdivision-multiplexing (WDM), Rayleigh backscattering (RB) noise mitigation, long-reach, on-off keying.

A Simple WDM-PON Architecture Together With Private Interconnected ONUs

“…In addition to the use of optical fiber to transmit access signals, the FSO connection is also one of the ways as seen in Fig. 1(a), when some environmental limit or special consideration [14]. The VPN system does not necessarily need to be composed of all ONUs in practical state.…”

“…So, the related power budgets are 43, 42.5, 41 and 39.5 dB, respectively. The redundant budgets of 22, 21.5, 20 and 18.5 dB can be used to estimate the free space transmission length between OWU and ONU without using optical amplification for optimal design[14]. In addition, the insets of Fig.6are the observed eye diagrams of four selected wavelengths at the smallest received powers, respectively.…”

A Survivable and Flexible WDM Access Network by Alternate FSO- and Fiber-Paths for Fault Protection

“…1(a) and 1(b). In the demonstration, due to two different downstream and upstream wavelengths in the WDM-PON system, the Rayleigh backscattering (RB) beat noise also can be avoided [10]. To achieve self-healing protection, each ONUR and ONUB can be connected by the SMF-or FSO-based link to prevent the fiber breakpoint occurring between RN and ONU, as viewed in Fig.…”

Symmetry 28 Gbps/λ WDM Access Network Together With Confidential Connection Between Two Specific Clients

“…If the downstream and upstream signals utilize the same wavelength for bidirectional connection, it would cause the Rayleigh backscattering induce interference noise at the photodiode (PD) of optical line termination (OLT) and ONU, respectively [13]. To prevent the RB noise in WDM access, using the wavelength-shift modulation scheme at each ONU [14], dual wavelength bands for data division [15][16][17] and various fiber access architecture [18,19] have been studied and discussed. In some cases, once two specific ONUs require confidential or personal signal connection and does not go through the OLT, a specific fiber deployment and additional transceiver (TRx) module are demanded to link the two ONUs [17,18].…”

“…To prevent the RB noise in WDM access, using the wavelength-shift modulation scheme at each ONU [14], dual wavelength bands for data division [15][16][17] and various fiber access architecture [18,19] have been studied and discussed. In some cases, once two specific ONUs require confidential or personal signal connection and does not go through the OLT, a specific fiber deployment and additional transceiver (TRx) module are demanded to link the two ONUs [17,18]. However, if the private connection is changed to two certain ONUs, the fiber link also needs to relaying and increase the cost.…”