Puspa Devi Pukhrambam

Electroabsorption Modulated Lasers With High Immunity to Residual Facet Reflection by Using Lasers With Partially Corrugated Gratings

Residual facet reflection can significantly degrade the performance of electroabsorption modulated lasers (EMLs) operating at high data rates. This issue also complicates the fabrication and characterization of the highly demanded light sources for optical interconnects and transmission. It is desired to optimize the device structure to make EMLs robust and immune to residual facet reflection. EMLs with a partially corrugated-grating DFB section are designed and optimized to have much improved tolerance to the residual optical reflection from the modulator output facet. By designing the laser section with an appropriate grating length and linear gain coefficient, the EML can have good tolerance to residual facet reflection. The analysis indicates that 100% yield can be obtained with the optimal design. If the EML needs to operate over a wide ranges of gain coefficient and facet reflection, >70% of yield can still be obtained.

Practical aspects of access network indoor extensions using multimode glass and plastic optical fibers

Following the successful installation of optical fibers in the access network, the next current step is to extend the optical fiber network into buildings to satisfy the ever-growing demand for broadband services. Low-cost easily installable multimode glass and plastic optical fibers are attractive media for high-capacity indoor telecom networks. Many existing buildings already have glass multimode fibers installed for local area network applications. New developments of plastic optical fibers with low losses in the 850–1300-nm range have spawned a great interest in using these fibers for indoor applications together with glass multimode fibers. Several issues arise in these interconnections, such as large variations in connector losses among randomly selected fiber segments, asymmetric link losses in bidirectional links, and variations in bandwidths among different types of fibers. In this paper we examined real-world link losses when randomly interconnecting multimode glass and plastic fiber segments having factory-installed connectors.

Convergence of energy management data with optical access networks by sharing the fault-monitoring channel

A converged optical access network system is proposed to provide reliable transmission for both communication data and energy management data. The convergence is carried out by a novel multifunction and low-cost fault-monitoring scheme in passive optical network systems. The scheme enables monitoring the occurrence of damages to distribution fibers, identifying the status of ONUs, localizing damaged fibers, and transferring smart meter data over the fault-monitoring channel. The use of a simple tone detection technique can help the recognition of a fiber break among distribution fibers and activation of the smart meter data transmission. Transmission of smart metering data over the fault-monitoring channel with a 10 Mb/s data rate is demonstrated. Both the added tone detection and upstream smart meter data transmission have a relatively large loss budget and will not affect the design of the original optical access networks.

Converging optical access with energy management networks to provide bidirectional services

We propose a converged access network for servicing various applications in smart buildings and cities. The network convergence aims to share equipment and energy by transmitting bidirectional smart grid data over the fault monitoring channel in the passive optical network systems. The proposed scheme can successfully transfer 100 Mb/s smart meter data over the fault-monitoring channel. It can provide both energy-efficient real-time and non-real-time smart services and enhance channel fault monitoring simultaneously. Energy savings of up to 80% can be achieved for each ONU. The scheme successfully supported > 105 devices for smart meters data for each ONU.

Performance enhancement of radio-over-fiber system by optical injection locking of a directly modulated semiconductor laser

We investigated experimentally the effects of optical injection locking on the performance of a directly modulated semiconductor distributed feedback laser, aiming for radio-over-fiber (RoF) applications. The resonance frequency and noise level are measured at various frequency detuning and external injection ratios. Under optical injection locking with a -2.9dB injection ratio and -12.5GHz detuning, the resonance frequency improved 2.81 times and noise level at the peak reduced by 3.5dB compared to a free running laser. We also achieved 5dB dynamic range enhancement with the same injection conditions. A resonance frequency improvement of 4.2 times was achieved with increased detuning. Performances of a ROF system were evaluated at RF frequencies of 2, 2.5 and 3GHz using a 64-QAM signal. From the error vector magnitude measurements, the optical injection locking can both enhance the linearity and reduce the noise for direct modulation, and thus extending the dynamic range of input RF signals.