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In this paper, a spectrally coded optical code division multiple access (OCDMA) system using a hybrid modulation scheme has been investigated. The idea is to propose an effective approach for simultaneous improvement of the system capacity and security. Data formats, NRZ (non-return to zero), DQPSK (differential quadrature phase shift keying), and PoISk (polarisation shift keying) are used to get the orthogonal modulated signal. It is observed that the proposed hybrid modulation provides efficient utilisation of bandwidth, increases the data capacity and enhances the data confidentiality over existing OCDMA systems. Further, the proposed system performance is compared with the current state-of-the-art OCDMA schemes. [ABSTRACT FROM AUTHOR]

In this paper, security of the spectrally encoded-optical code division multiplexed access (OCDMA) system is enhanced by using 2-D (orthogonal) modulation technique. This is an effective approach for simultaneous improvement of the system capacity and security. Also, the results show that the hybrid modulation technique proved to be a better option to enhance the data confidentiality at higher data rates using minimum utilization of bandwidth in a multiuser environment. Further, the proposed system performance is compared with the current state-of-the-art OCDMA schemes. [ABSTRACT FROM AUTHOR]

Highlights: [•] The influence of crosstalk induced by hybrid optical amplifiers has been examined. [•] It is observed that as the input power increases the crosstalk will also increase. [•] It is recommended that R–E is the best combination as compared to other HOA. [•] The investigation of crosstalk has also been done in 16 channel DWDM system. [ABSTRACT FROM AUTHOR]

• A novel remote node design has been presented with fiber fault protection for ring topology NG-PON2. • The presented NG-PON2 architecture is based on single fiber ring topology. • The proposed remote nodes are able to communicate in both clockwise and anticlockwise directions. • In case of fiber fault the remote nodes can change the direction of communication and service disruption can be avoided. The service disruptions in passive optical networks (PONs) due to fiber or node failure is an important issue. In the conventional star topology time and wavelength division multiplexing (TWDM) based next generation passive optical network stage 2 (NG-PON2), there is no provision to restore the service if the fiber between remote node (RN) and optical network unit (ONU) fails. In this paper, we proposed a novel entirely passive node design for ring based NG-PON2 which provides fiber fault protection against any fiber break between RNs. The working of the proposed node is verified by simulating normal conditions and fault conditions. It is observed that in the case of fiber failure, the affected ONUs can still communicate with the optical line terminal (OLT). The performance of the system has been analyzed in terms of bit error rate (BER), and the BER <10−9 confirms the correct working of the system. [ABSTRACT FROM AUTHOR]