Multimode interference photonic switches

Photonic switches are becoming key components in advanced optical networks due to their various applications in optical communication. One of the key advantages of photonic switches is the fact that they redirect or convert light without any optical to electronic conversions and vice versa. As one type of optical switch, multimode interference (MMI) switches have received more attention in recent years due to their significant role. The structure and operation principle of various types of MMI switches are introduced, and the recent progresses of MMI switches are also discussed

A ridge waveguide for thermo-optic application

A thermal analysis and structure of a ridge single mode waveguide with a metal heater are presented. The steady-state temperature increases linearly and the thermal response becomes slower at the same power consumption, when the under-etched depth in the lower cladding increases. When the upper cladding thickness decreases, the thermal response becomes faster. This shows that a thinner upper cladding and a deeper etching are preferred to achieve a faster thermal response and lower power consumption, respectively. The numerical simulation also shows the power consumption of the present ridge waveguide is almost third of that for conventional one and the response time is half of that of the conventional one

Fabrication and characterization of polymer thermo-optic switch based on MMI coupler

The 2×2 polymer thermo-optic switch based on MMI coupler is realized. This device is fabricated using standard fabrication techniques such as coating, photolithography, and dry etching. A crosstalk level of -36.2 dB is achieved at cross and bar states. A power consumption of 1.85 mW is applied to change the state of the switch from the cross to the bar state. A switching time of less than 0.7 ms is traced to change a state of the realized switch

Thermo-optic multimode interference switches with air and silicon trenches

A novel thermo-optic multimode interference (MMI) switch with air and silicon trenches was proposed, and the performance of the switch was simulated. In the design, one heating electrode is used to alter the refractive index at a spot image which changes the phase of this image to realize the switching function. The simulation results clearly indicate that the MMI switch can satisfy −39 dB crosstalk at two states. The electric power consumption for the MMI switch with these trenches is less than half of that of a conventional MMI switch

Bandwith efficient hybrid wireless-opical broadband-access network (WOBAN) based on OFDM transmission

In this paper, a simple and bandwidth efficient hybrid wireless-optical broadband access network (WOBAN) based on orthogonal frequency division multiplexing (OFDM) is pro- posed and designed. It is an optimal combination of an optical backhaul and a wireless front-end for an e±cient access network. The bandwidth e±cient WOBAN based on OFDM provides an effective solution to eliminate intersymbol interference (ISI) caused by dispersive channels. There are two factors considered important here; multipath fading in wireless link and dispersion effects in fiber link. The physical layer performance is analyzed in terms of bit error rate (BER), error vector magnitude (EVM), and signal-to-noise ratio (SNR). An 8 Gb/s data rate has been achieved by the optical backhaul along optical ¯ber length of 20 km. The wireless front-end access point supports data rate up to 240 Mb/s along an outdoor wireless link

Coexistence of OFDM-Based IMT-Advanced and FM Broadcasting systems

Coexistence analysis is extremely important in examining the possibility for spectrum sharing between orthogonal frequency-division multiplexing (OFDM)-based international mobile telecommunications (IMT)-Advanced and other wireless services. In this letter, a new closed form method is derived based on power spectral density analysis in order to analyze the coexistence of OFDM-based IMT-Advanced systems and broadcasting frequency modulation (FM) systems. The proposed method evaluates more exact interference power of IMT-Advanced systems in FM broadcasting systems than the advanced minimum coupling loss (A-MCL) method. Numerical results show that the interference power is 1.3 dB and 3 dB less than that obtained using the A-MCL method at cochannel and adjacent channel, respectively. This reduces the minimum separation distance between the two systems, which eventually saves spectrum resources

Crosstalk improvement of a thermo-optic polymer waveguide MZI-MMI switch

A 2 × 2 MZI-MMI switch based on thermo-optic effect with a ridge in the silicon substrate was proposed and the performance of switch was simulated. The main purpose behind this change in substrate layer is to localize the heating at a heated arm single mode waveguide and limit the increasing temperature at a second one. The switch performance of the device should be improved, compare to the usual one. Using finite difference beam propagation method (FD-BPM) and thermal computing simulation based on finite element method (FEM), the results clearly indicate that the MZI-MMI switch can satisfy -31 dB crosstalk at two states

Cosine bend-linear waveguide digital optical switch with parabolic heater

A new digital optical switch (DOS) with large branching angle and short device length that exhibits low crosstalk and low power consumption is demonstrated. The Y-branch shape was optimized by introducing constant effective refractive index difference between branches (?Neff) along the propagation direction through beam propagation method (BPM) scheme. To provide decreasing local branching angle that results in the improvement of the crosstalk, two modified cosine bend was introduced to form the Y-branch. The modified cosine branch was then connected to a linear branch. The heater electrode was optimized so that the temperature fields induce a constant ?Neff to satisfy initial assumption in designing the Y-branch shape. With branching angle of 0.299° and device length of only 5 mm, the simulation shows that the device could exhibits crosstalk of -33 dB at calculated required power of only 26 mW

Cost-effective 2.5 gb/s bidirectional WDM pon using single optical source at the central office

Nowadays, the bandwidth demand of the telecommunication network is growing rapidly due to the increasing number of technology-intelligent users. Optical broadband access networks have emerged to address two issues: (1) channel capacity sharing fairly to the customers, and (2) adequate capacity assignment according to service requirements. The wavelength division multiplexing passive optical network (WDM PON) is a promising solution to provide high data rate, excellent scalability, good protocol transparency and easy upgradability. In this paper, a cost-effective bidirectional WDM PON is proposed to provide symmetrical 2.5 Gb/s by using just single optical laser diode (LD) at the central office (CO). The optical frequency upconversion (OFU) technique is used to implement the proposed network. At the optical network unit (ONU), the reflective semiconductor optical amplifier (RSOA) reuses and amplifies the downlink wavelength to modulate the upstream data. The bit error rate (BER) performance and eye diagrams of the designed system are investigated