Advanced metro-access WDM optical fiber telecommunication networks use integrated wavelength switching nodes to provide efficient, flexible wavelength allocation along the link. Recent developments, together with the increase in bandwidth intense applications, have sparked great interest in flexible, grid-like optical network systems. Flexible spectrum optical network systems with nonstatic channel bandwidth, wavelength allocation, switching, and routing permit the optimum distribution of data with variable rates and modulation formats. We describe a unique technique for all-optical wavelength reservation at a forwarding flex spectrum node. The outgoing signal is locked to the incoming signal at the node, thereby guaranteeing automatic wavelength reservation and allocation. A saturated erbium-dope fiber amplifier (EDFA) is used to erase data from the incoming signal, which is then used to lock the wavelength of the forwarding node through vertical cavity surface emitting laser injection. The EDFA is shown to reduce the extinction ratio of the incoming signal from 7.3 dB to less than 1 dB (560 mdB). We show automatic wavelength reservation over 1.68 nm within the C-band, with 25.5-km transmission over G. 655 single mode fiber. Considering 50-GHz per-channel bandwidth allocations, this technique translates to four-channel operation in a typical metro-access type configuration.
The exponential growth of data traffic in current optical communication networks require higher capacity for the bandwidth demands at a reduced cost per bit. All-optical signal processing is a promising technique to improve network resource utilization and resolve wavelength contention associated with flexible spectrum. This is achieved without necessarily employing optical to electrical signal conversions. In this paper, we experimentally present a novel, spectral efficient technique for defragmentation and wavelength switching on a cascade of vertical cavity surface emitting lasers (VCSELs). This is based on cross gain modulation of the optical transmitter. A 10 Gbps intensity modulated master VCSEL lasing at 1549 nm was used for optical power injection into the side modes of two slave VCSELs. The injection results in energy transfer between the lasing modes, causing data inversion on the transmission wavelength. The master lasing wavelength was tuned from 1546.5 to 1551.7 nm resulting in a 5.2 nm or 650 GHz spectral width by varying the bias current. A total of 9 continuous 50 GHz spaced WDM channels with nonoverlapping nominal frequencies and uniform guard bands were generated. This can be used to attain seamless defragmentation and bandwidth optimization for effective spectral resource management. The novel technique is flexible in terms of modulation formats and accommodates various formats with spectrally continuous channels, thereby fulfilling the future bandwidth demands with transmissions beyond 100 Gbps per channel while maintaining spectral efficiency.
Real-time wavelength switching and routing at key access network nodes is an emerging fundamental functionality requirement for transparent content resolution and wavelength assignment towards better utilization of network resources under dynamic traffic patterns. In this paper, we experimentally demonstrate the first vertical cavity surface emitting laser (VCSEL)-based broadband switch for ultra-wide wavelength data traffic routing in Datacom. An 850 nm multimode VCSEL is directly modulated with 8.5 Gbps data and successfully transmitted error free over 100.3 m of OM3 multimode fibre link. At the integration node, the received data signal is used to drive a second VCSEL at 1550 nm, and forwarded over a second network link over 24.7 km of single mode fibre. We therefore achieve the first reported all-optical, real-time, inter-band wavelength switch to C-band. By exploiting wavelength tuneability, the 1550 nm VCSEL-based forwarding node is tuned to over 3.2 nm spectral range, for ultra-wide data routing over the second network link. A receiver sensitivity of -14.28 dBm of the converted signal is achieved at back-to-back analysis at the integration node. An additional penalty of 2.72 dB is introduced over the 24.7 km of single mode fibre transmission link. This work offers a viable enabling development technology for broadband wavelength converters for application real-time wavelength routing in the access network, to address content resolution and wavelength assignment problem for current and future Datacom.
Advanced metro-access WDM optical fibre telecommunication networks employ integrated wavelength switching nodes to provide efficient, flexible wavelength allocation along the link. Recent developments, together with the increase in bandwidth intense applications, have sparked great interest in flexible, grid-like optical network systems. Flexible spectrum optical network systems with non-static channel bandwidth, wavelength allocation, switching and routing permit the optimum distribution of data with variable rates and modulation formats. This paper describes a unique technique for all-optical wavelength reservation at a forwarding flex spectrum node. The outgoing signal is locked to the incoming signal at the node, thereby guaranteeing automatic wavelength reservation and allocation. A saturated EDFA is used to erase data from the incoming signal, which is then used to lock the wavelength of the forwarding node through VCSEL injection. The EDFA is shown to reduce the extinction ratio of the incoming signal from 7.3 dB to less than 1 dB (560 mdB). We show automatic wavelength reservation over 1.68 nm within the C-band, with 25.5 km transmission over G. 655 single mode fibre. Considering 50 GHz per-channel bandwidth allocations, this technique translates to 4-channel operation in a typical metro-access type configuration.
For the first time, we demonstrate, VCSEL-to-VCSEL wavelength conversion within the low attenuation 1550 nm window, including transmission over fibre and bit error rate (BER) performance characterization. We experimentally demonstrate a low injection power optical wavelength conversion by injecting an optical beam from a signal carrier master vertical cavity surface-emitting laser (VCSEL) into the side-mode of the slave VCSEL. This technique solves the challenge of wavelength collisions and also provides wavelength re-use in typical wavelength division multiplexed (WDM) systems. This paper, for the first time, uses two 1550 nm VCSELs with tunability range of 3 nm for a 5-9.8 mA bias current. The master VCSEL is modulated with a non-return-to-zero (NRZ) pseudo-random binary sequence (PRBS_27-1) 8.5 Gb/s data. A data conversion penalty of 1.1 dB is realized when a 15 dBm injection beam is used. The transmission performance of the converted wavelength from the slave VCSEL is evaluated using BER measurement at a 10-9 threshold. A 0.5 dB transmission penalty of the converted wavelength data is realized in an 8.5 Gb/s transmission over 24.7 km. This work is vital for optical fibre systems that may require wavelength switching for transmission of data signals.
Access networks based on vertical cavity surface emitting laser (VCSEL) transmitters offer alternative solution in delivering different high bandwidth, cost effective services to the customer premises. Clock and reference frequency distribution is critical for applications such as Coordinated Universal Time (UTC), GPS, banking and big data science projects. Simultaneous distribution of both data and timing signals over shared infrastructure is thus desirable. In this paper, we propose and experimentally demonstrate a novel, cost-effective technique for multi-signal modulation on a single VCSEL transmitter. Two signal types, an intensity modulated 10 Gbps data signal and a polarization-based pulse per second (PPS) clock signal are directly modulated onto a single VCSEL carrier at 1310 nm. Spectral efficiency is maximized by exploiting inherent orthogonal polarization switching of the VCSEL with changing bias in transmission of the PPS signal. A 10 Gbps VCSEL transmission with PPS over 11 km of G.652 fibre introduced a transmission penalty of 0.52 dB. The contribution of PPS to this penalty was found to be 0.08 dB.
Precise and accurate timing signals distributed between a centralized location and several end-users are widely used in both metro-access and speciality networks for Coordinated Universal Time (UTC), GPS satellite systems, banking, very long baseline interferometry and science projects such as SKA radio telescope. Such systems utilize time and frequency technology to ensure phase coherence among data signals distributed across an optical fibre network. For accurate timing requirements, precise time intervals should be measured between successive pulses. In this paper we describe a novel, all optical method for quantifying one-way propagation times and phase perturbations in the fibre length, using pulse-persecond (PPS) signals. The approach utilizes side mode injection of a 1550nm 10Gbps vertical cavity surface emitting laser (VCSEL) at the remote end. A 125 μs one-way time of flight was accurately measured for 25 km G655 fibre. Since the approach is all-optical, it avoids measurement inaccuracies introduced by electro-optical conversion phase delays. Furthermore, the implementation uses cost effective VCSEL technology and suited to a flexible range of network architectures, supporting a number of end-users conducting measurements at the remote end.
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