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In this paper, the surface roughness characteristic of D-shaped optical fibre sensors with its effects on the sensitivity has been studied. The ULTRAPOL end and edge polishing system was used with some modifications to fabricate the D-shaped sensors with planar sensing zone from the single-mode optical fibres. The mean surface roughness of 343, 96, 25 and 9 nm was estimated at the sensing zone of the D-shaped sensors which were sequentially polished with 30, 9, 3 and 0.5 µm grit size polishing films, respectively. From the experimental results, it has been observed that surface roughness of the sensing zone does not exhibit the significant effects on the output signal strength, whereas the sensitivity of the D-shaped sensors nonlinearly related with the surface roughness of the sensing zone. The designed D-shaped optical fibre sensors have potential applications in biomedical and chemical industries.

A fiber optic sensor for monitoring mercuric (Hg2+) ions in the aqueous sample have been developed based on modified cladding. To fabricate a D-shaped sensing zone onto the multimode optical fiber lengthwise polishing was utilized using a mechanical end and edge polishing system. The produced sensing region has dimensions of 10 mm × 125 μm × 62 μm (l × w × h). A 2 μm thin layer of Al2O3 nanoparticles sensitized with 4-(2-pyridylazo)-resorcinol was deposited onto the sensing element of multimode fiber optic sensor to make it sensitive and selective for Hg2+ ions. The analytical results demonstrate that the sensing device has a linear response for Hg2+ ions concentration over a range from 4 to 16 ppm along with a 4 ppm limit of detection in an aqueous sample at room temperature. The selectivity of the sensor is examined for the recognition of Hg2+ ions in presence of other cations such as zinc and/or lead ions up to 16 ppm in an aqueous solution. The main merits of this fabricated sensor are easy and safe installation, rapid response, enhanced linear response range, and better selectivity towards Hg2+ ions.

A new four-wave mixing scheme to practically measure the non-linear coefficient of fibers is introduced. A single erbium-doped fiber amplifier is used to create the two wavelengths for the four-wave mixing inputs, which are pre-spectrally sliced via fiber Bragg grating filters. The proposed scheme avoids the Brillouin backscattering, rendering this a more accurate method to determine fiber nonlinearities than conventional coherent FWM systems. Furthermore, the generated FWM seed beams are pure and ultra-narrow, and can therefore be treated as coherent light. Consequently, accurate degeneracy factor can also be taken into consideration.

Next-generation (NG) access networks require simultaneous provision of wired and wireless services and high data rates to meet the large demands of mobility and multiple services. In this paper, we propose a novel spectral efficient radio over fiber (RoF) scheme to simultaneously provide two spatially multiplexed multiple input multiple output (MIMO) wireless signals with a baseband (BB) wired signal in one wavelength using a centralized light source. The proposed scheme can be applicable to wavelength division multiplexed passive optical networks (WDM-PONs). The BB signal is modulated at a low extinction ratio (ER). The modulated light is re-used to modulate two MIMO signals that have the same carrier frequency that is combined optically using polarization-division-multiplexing (PDM). The data rate for each MIMO stream was 1.25 Gb/s, and the data rate was 2.5 Gb/s for the BB signal. Error free performance with a bit error rate (BER) of 10 −9 was achieved for all three signals after 20 km and 60 km through single mode fiber (SMF) for 16-QAM and 4-QAM for the MIMO signals, respectively.

The generation of tunable multiwavelength erbium-doped fiber laser based on an integrated structure of a single-core comb filter and nonlinear polarization rotation (NPR) is proposed and successfully demonstrated at room temperature. The NPR effect effectively induced intensity and wavelength-dependent loss to alleviate mode competition caused by homogeneous gain broadening in erbium-doped fibers. Thirty-two lasing wavelengths in a 3 dB flattened spectrum with a tunable wavelength spacing of 0.9 nm–1.8 nm have been achieved. Good stability of the laser operating at room temperature has been verified by using an optical spectrum analyzer to measure every 10 min for an hour.

Free Space Optics (FSO) or optical wireless systems provide high data rate solution for broadband communication applications. FSO links are highly weather-dependent because different weather conditions significantly affect the link availability. In order to determine the best operational limit of an FSO link with respect to temperature and humidity, the effect of temperature and humidity on FSO network is studied in this work. Two new equations are proposed to model the effect of temperature and humidity on an FSO link operating at 850 nm in tropical climate. The first equation is developed to model the relationship between the humidity and temperature for tropical regions, while the second equation models the FSO link attenuation in terms of tropical temperature. In conclusion, it is suggested that FSO links can be operated with a normal variation of temperature and humidity in a tropical country to achieve near carrier class availability.

This work describes a polarization-insensitive four-wave mixing undertaken with a fast semiconductor optical amplifier that acted as a nonlinear medium. The pump output was composed of coherent light, while the probe element received incoherent amplified spontaneously emitted light that had been spectrally-sliced via an ultra-narrow band fiber Bragg grating filter. An analytical model was utilized to evaluate the speed of the semiconductor optical amplifier via extracted nonlinear parameters that were relevant to the experimental results.

A new fabrication method is introduced for the production of D-shaped optical fiber. A mechanical end and edge polishing system with aluminum oxide polishing film is utilized to perform sequential polishing on one side (lengthwise) of single-mode optical fiber in order to obtain a D-shaped cross section. Adjusting specific mechanical parameters allows for control of the volume of the D-shaped zone, while the fiber surface smoothness is governed by selection of polishing film grit size. To meet the accuracy and repeatability requirements, optical power loss is monitored during the entire polishing process in situ and in real time. This proposed technique possesses advantages of rapidity, safety, simplicity, repeatability and stability with high precision in comparison with contemporary methods for production. Sensor performance tests on the fiber reveal a linear response with linearity up to R2 = 0.984 for surrounding refractive index in the range of 1.320–1.342 refractive index, which corresponds to diffe...

This paper details a proposal and successful demonstration of an ultra-narrow and very high optical signal-to-noise ratio wavelength converted channel that was generated from an efficient ultra-narrow pre-spectrum sliced probe channel via four-wave mixing in a highly non-linear fiber medium. An array of narrowband fiber Bragg grating filters acted as a discriminative component to pre-spectrum slice the probe channel from backward amplified spontaneous emission, which, in turn, induced an additional fiber Bragg grating filtering mechanism within an erbium-doped fiber medium in a saturable configuration. A resultant optical signal-to-noise ratio of more than 70 dB in the probe channel gave rise to a 40 dB optical signal-to-noise ratio in the converted channel. These outcomes indicate the proposed scheme is highly suitable for practical, cost-effective wavelength conversion in any “pre-spectrum sliced” optical communication system.

Next-generation access networks require provision of wireless services and high data rate to meet the huge demands for mobility and multiple services. Moreover, reusing the currently deployed optical distribution networks (ODNs) is highly beneficial and cost effective for providing the new high data rate wireless demands. In this paper, bidirectional radio over fiber passive optical network (RoF-PON) capable of handling multiple-input–multiple-output (MIMO) streams at low cost, high spectral efficiency and backward compatibility with currently deployed PON, is proposed. To the best of our knowledge, all the existing RoF MIMO solutions have not considered compatibility with currently deployed ODNs. Eight laser diodes (LDs) at the central office (CO) are enough for the whole system, instead of having LD or optical transmitter at each remote antenna unit (RAU), which makes a colorless and cost-effective RAU. Twenty four wavelengths are generated using optical comb technique. Each two 16-QAM MIMO signals that have the same carrier frequency in the downstream (DS) transmission are optically combined using polarization-division-multiplexing (PDM), where each two upstream (US) MIMO signals are time division multiplexed. The PDM configuration doubles spectral efficiency with a power penalty of only 1.5 dB. The proposed architecture is a bidirectional asymmetric RoF-PON with total 40/10 Gb/s for DS/US transmission. Even after transmission over 20 km SMF and splitting ratio of 32, acceptable transmission performance and widely separated constellation diagrams for the 16-QAM signals are achieved, with bit error rate (BER) of 10−6 for DS signals and 10−3 for the US signals which can be reduced down to 10−6 by using forward error correction (FEC).

The second stage of next-generation passive optical network (NG-PON2) based on time and wavelength division multiplexed passive optical network (TWDM-PON) was proposed by a telecommunication group research to enhance the performance of broadband access networks. TWDM-PON was selected as the best candidate for NG-PON2 solution because of its ability to support the NG-PON2 requirements, such as enhanced bandwidth capacity, 40Gb/s, and coexistence with previously existing generations without any change to optical distribution network (ODN). This paper reviewed the recent progress carried out on a TWDM-PON system configuration, with emphasis on tunable transmitter and receiver optical network unit (ONU) in terms of the amount of tuning range reported in exploiting the wavelength plan provided with cost efficiency. The speed of data rate transmitted on the downstream and upstream links between optical line terminal (OLT) and ONU with the way of stacking approach in NG-PON2 is reviewed. In addition, the power system budget is reviewed to determine the number of users allocated with the system with each transmission allowed.

Hybrid wavelength division multiplexing/multibeam free-space optics (FSO) is a promising technique to overcome atmospheric attenuation due to tropical rain and to fulfill the growing demand for increased communication bandwidth and scalability. In this study, a hybrid four channel 1.25-Gb/s WDM/multibeam FSO network having four wavelengths with standard downlink channel spacing of 0.8 nm (100 GHz) is proposed. The hybrid WDM/multibeam FSO technique improved the performance of an FSO link in terms of the received power, link distance, data rate, and scalability. The proposed technique provided access data to four end users, each at a data rate of 1.25 Gb/s along an FSO link distance of 1,100 m.

Current passive optical networks (PONs) (Gigabit PON (GPON) and Ethernet PON (EPON)) will run out of bandwidth sooner or later due to the ever increasing bandwidth demand. The aforementioned and the new next generation PON stage 1 (NG-PON1) standards (10 Gigabit-PON (XG-PON) and 10 Gigabit Ethernet-PON (10G-EPON)) are based on time division multiplexing (TDM-PON), which has its limitations such as limited bandwidth. In this paper, hybrid TDM–WDM PON and stacked TDM-PON architectures are evaluated and compared as solutions for NG-PON stage 2 (NG-PON2). Both architectures are fully capable of satisfying the requirements of NG-PON2. Stacked TDM-PON has the advantage of being compatible with the currently deployed optical distribution network (ODN). Considering four wavelengths and 10 Gb/s/wavelength, the hybrid TDM–WDM PON does not seem to offer noticeable advantages over stacked TDM-PON.

The fiber-wireless (FiWi) access network is a prestigious architecture for next generation (NG) access network. NG access networks are proposed to provide high data rate, broadband multiple services, scalable bandwidth, and flexible communication for manifold wireless end-users (WEUs). In this paper, the FiWi access network is designed based on a wavelengths division multiplexing/time division multiplexing passive optical network (WDM/TDM PON) at the optical backhaul with data rate of 2.5 Gb/s and wireless fidelity-worldwide interoperability for microwave access (WiFi–WiMAX) technologies at the wireless front-end along a 50 m–5 km wireless links with data rate of 54–30 Mb/s, respectively. The performance of the optical backhaul and the wireless front-end, in the proposed FiWi access network, has been evaluated in terms of bit error rate (BER), error vector magnitude (EVM), and signal-to-noise ratio (SNR) of the physical (PHY) layer. The scalability of the optical backhaul based on maximum split ratio of 1/32 for each wavelength channel and a fiber length of 24 km from the central office (CO) to the access point (AP) is analyzed with bit error rate (BER) of 10−9.

We propose and experimentally demonstrate switchable and tunable transmission characteristics of a single-core comb filter based on thermal operation. Its temperature characteristics are investigated to reveal a shift in the peak wavelength position from 0.15 to 0.41 nm/°C and a tunable range of wavelength spacing of 1.18–1.38 nm for maximum and minimum effective lengths, respectively. This configuration provides the unique advantages of an all-fiber structure, tunable wavelength spacing, switchable spectral peaks, independent tuning of the center wavelength and wavelength spacing of the spectral peaks, and low polarization sensitivity. It is relatively simple to fabricate and is expected to have applications in temperature fiber optic sensors and multiwavelength fiber laser sources.

The elastic characteristics of linear birefringence and its effect upon the output of an optical fiber dual-pass MZI comb filter are theoretically and experimentally analyzed. The result shows that the linear birefringence is induced by the mutual pressure applied on fiber due to the applied stress. As a result of induced birefringence, the peak wavelength shifts continuously with the continuous change in stress up to a certain value of the applied stress. But for discrete change in stress the peak wavelength shifting is not continuous. Theoretically, the gradients of peak wavelength position shifting 0.16 nm/N and 0.36 nm/N are calculated for the maximum and minimum effective length respectively. Experimental observations of the gradients acquire values of 0.14 nm/N and 0.40 nm/N. These results might be useful for pressure sensing technique.

We propose and experimentally demonstrate switchable and tunable transmission characteristics of a Mach–Zehnder interferometer comb filter based on thermal operation. Its temperature characteristics are investigated to reveal a shift in the peak wavelength position from 0.003 to 0.004 nm/°C and a tunable range of wavelength spacing of 0.76–0.90 nm for maximum and minimum effective lengths, respectively. This configuration provides the unique advantages of an all-fiber structure, tunable wavelength spacing, switchable spectral peaks, independent tuning of the center wavelength and wavelength spacing of the spectral peaks, and low polarization sensitivity. It is relatively simple to fabricate and expected to have applications in temperature fiber optic sensors and multiwavelength fiber laser sources.

The bandwidth demand of telecommunication network is growing rapidly due to the increasing number of technology-intelligent end-users. The emerging optical and wireless access networks are continuously competing with each other to provide these requirements for the end-users. The optical access networks provide huge data rate and long-distance link, but it is less ubiquitous. The wireless access networks provide flexible and ubiquitous communication with a low deployment cost. However, its deployment scalability is limited by the spectrum and range limitations. The hybrid wireless optical broadband access network (WOBAN) is a powerful combination of optical backhaul and wireless front-end to contribute to a good scalability, cost effective and flexible communication system. This paper reviews the key enabling access technologies and progress advancements of these networks. The emerging optical and wireless access technologies are also presented and compared.

Free space optics (FSO) is a promising communication technique for various types of services in the optical access network. Single beam FSO system in tropical rainy weather is vulnerable to atmospheric rain attenuation, so it is necessary to have precise power law parameters of rain attenuation in tropical regions. In this study, the power law parameters k , and α are estimated as 2.03 and 0.74, respectively for the FSO applications in tropical South-East Asian weather. These parameters were evaluated by using least square mean equation (LSME) method with Levenberg–Marquardt optimization based on the one year collected heavy rain data. The obtained parameter values for tropical weather are contributed to improve link performance for high-speed networks.

Free space optics (FSO) has attracted a lot of attention for a variety of applications in telecommunications area, and it is dream of every researcher and telecommunication society to make it a real alternative solution for the last mile problem, to replace fiber optics. FSO is much preferred because of its low maintenance cost and deployment time. FSO with single-beam system is vulnerable to atmospheric attenuation, so to overcome this, a multiple-beam FSO transceiver system has become prominent and is usually used. In this paper, average rain attenuation is evaluated from the collected rain intensity data which are collected for a period of seven months, and implemented in the study concerning results relating link distance, and received optical power of using multiple-beam FSO system in tropical rainy weather. Comparison is made in terms of received optical power, geometrical losses, atmospheric losses, and bit error rate (BER) on using different number of optical beams, based on simulation at data rate of 1 Gb/s. From the results it is clear that the quality of received power is improved by using up to four beams, along with link distance up to 1141.2 m as compared to one-beam, two-beam, and three-beam, with link distances 833.3 m, 991.0 m, 1075.4 m, respectively.

An optimization process of specialized heater electrode design for a Multimode Interference (MMI) based polymer in silica thermo-optical switch is described. The switch is designed based on the waveguide structure of photodefinable BenzoCyclobutene (BCB 4024-40) polymer core, sandwiched by a 6 μm thickness of silica (SiO 2 ) upper clad layer and BK7 glass as a substrate. The upper clad thickness has been chosen such that to avoid any attenuation due to lossy behavior of the metal electrode. The light path is controlled by embedded thermal heater on top of the waveguide at specified location. Starting from a straight rectangular heater at pre-designed location, a migration technique and optimization toward a trapezoidal heater structure has been proposed which utterly claimed a significant improvement in terms of tuning power by more than 15%.

Hybrid gigabit-passive optical network (GPON) is a hybrid passive optical network, where wavelength division multiplexing (WDM) GPON and time division multiplexing (TDM)-GPON are integrated into a single passive optical network, reducing cost and increasing the data rate. In this paper, 2.5 Gb/s GPON downstream link is presented, using the radio over fiber (RoF) technique in GPON network architecture. It has been done by means of commercial OptiSystem simulation software, where, differential phase shift keying (DPSK) modulation is proposed by using 2.4 GHz radio frequency. The propagation of radio signals along a 25 km standard single mode fiber (SMF) investigated. The simulated model can support 32 and 64 users. The analysis was made based on the performance of eye diagram, optical signal to noise ratio (OSNR), constellation diagram, error vector magnitude (EVM) and received power.

A vinyltriethoxysilane (VTES) based hybrid organic–inorganic sol–gel is synthesized and characterized for its abilities in optoelectronic applications. The resulted hybrid material, which is known as VTT, is fabricated as a thin film structure under controlled environment. The film thickness for various coating speeds and refractive index are measured by the method of prism coupling. Based on the film characterization results, a 2 × 2 multimode interference photonic switch structure based on thermal controlling effect is proposed. A ridge waveguide of VTT in silica clad is used as a design structure. The switching characteristics due to changes in effective index are analyzed by the two-dimensional finite difference beam propagation method with transparent boundary condition. The proposed structure works well with low crosstalk level of −28 dB and low switching power relatively to the structural upper cladding thickness.

The fiber-wireless (FiWi) access network is a powerful hybrid architecture of optical backhaul and wireless front-end to support high data rates and throughput with minimal time delay. By using radio over fiber (ROF) technique, the optical fiber is well adapted to propagate multiple wireless services having different carrier frequencies. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber on the same wavelength, such as multi-input multi-output (MIMO) signals. A novel optical single-sideband frequency translation technique is designed and simulated to solve this problem. 240 Mb/s 802.11n MIMO signals are proposed to transport over FiWi system using the proposed approach at 2.4 GHz and 5.0 GHz carrier frequencies. The crosstalk between MIMO signals with the same carrier frequency is excluded, since each MIMO signal is carried on a specific optical wavelength. Error vector magnitude (EVM) values of −29.83 dB (for 2.4 GHz) and −28.41 dB (for 5.0 GHz) have been achieved for bit error rate (BER) 10−5 in the proposed FiWi system.

A D-shaped polarization-maintaining fiber (PMF) as fiber optic sensor for the simultaneous monitoring of strain and the surrounding temperature is presented. A mechanical end and edge polishing system with aluminum oxide polishing film is utilized to perform sequential polishing on one side (lengthwise) of the PMF in order to fabricate a D-shaped cross-section. Experimental results show that the proposed sensor has high sensitivity of 46 pm/µε and 130 pm/°C for strain and temperature, respectively, which is significantly higher than other recently reported work (mainly from 2013) related to fiber optic sensors. The easy fabrication method, high sensitivity, and good linearity make this sensing device applicable in various applications such as health monitoring and spatial analysis of engineering structures.

Optical chemical sensors have promoted escalating interest in the determination of various pollutants in the environment, which are creating toxicity and may cause serious health problems. This review paper focuses particularly on the recent progress and developments in this field; the working principles and basic classes of optical chemical sensors have been briefly described.

A research project has been established as a project conducted by the final year students individually. It is divided into two parts, Research Project I and Research Project II. The course is carried out for two semesters, at Semester VII and VIII of the study programme. To conduct this research project, every student is supervised by at least a lecturer. Research Project I covers the literature review for the selected title which is related with chemical and process engineering, the initial preparation and study of the project and report writing for the project task. At the end of the semester, students are asked to present a project proposal/project progress orally and in the form of a written report. This research project will then proceed to the Research Project II, which is performed in the following semester. This second project involves practical work, results and data analysis, discussion of the results, final report writing and oral presentation in a viva session. At the end of the semester, students are required to complete a dissertation/thesis and present the research outcomes orally in front of supervisors and the appointed examiner. To achieve the program outcomes for the program, an effort has been exerted to measure the Program Outcome (PO) based on the evaluation scheme of the Research Project II. Based on the PO mapping towards the Course Learning Outcome (CO), the PO assessed for this course covers almost all POs, which are 8 POs out of a total of 9 POs for both programmes. The mapping enables the PO assessment, based on the marks given for the POs. The data analysis obtained shows that students from both programmes have achieved around the scale of 3.7 up to 4 for all PO assessed, based on the Likert scale. This study illustrates the fact that PO can be indirectly deduced through the CO assessment. The obtained results also suggest that the PO achievement for the student has been regarded as encouraging and satisfactory.

Department of Chemical and Process Engineering (JKKP), Universiti Kebangsaan Malaysia has taken an initiative to implement an Integrated Project (IP) for Year II and III since the 2006/2007 session. This project combines three or four department offered compulsory courses each semester. Integrated project delivered to students is chemical/biochemical engineering problems with open solutions. This approach allows the application of generic skills of students such as leadership, work in teams, communicate orally and in writing and learn to find the current information through a process of lifelong learning. Student achievement in completing the Integrated Project has been measured and assessed through presentations and reports. This study was performed to measure the effectiveness of the Integrated Project implemented after four years in JKKP. Therefore, a questionnaire was distributed to the first batch of students who have been through fully integrated project while studying at JKKP, in a graduate friendly event at the end of their study. Analysis results of the effectiveness of the Integrated Project show that it has improved the confidence level in generic skills such as oral and written communication, teamwork, lifelong learning and the identification of current issues in students since it was firstly introduced in session 2006/2007. Positive feedback is also obtained from the students and they felt that Integrated Project should be continued in the future because it really helps them in completing design projects in the final year of their studies.

Feedback from the industrial stake holders indicates that soft skills such as communication, teamwork and independent learning are required from the graduates in addition to good technical competency. Traditional curriculum delivery through lectures, assignment and projects does not provide adequate opportunity and avenue for students to develop their soft skills. Innovation on the traditional curriculum delivery is required to make learning more interesting and provide opportunity for development of soft skills. The department of chemical and process engineering (JKKP), Universiti Kebangsaan Malaysia has been organizing Chem–E-Car competition since 2005 where student's participation is not mandatory and typically involves 2nd and 3rd year students. Students are given full freedom to choose their team member, to select the type of fuel or propulsion system and design their cars. These activities were carried out over a period of one and half month culminated with the Poster Presentation and Car competition. The top three teams that emerge winners from this competition represent UKM at the national level Chem-E-Car competition, an annual event organized by The Institution of Engineers Malaysia. The Chem-E-Car competition has been observed to provide opportunity for students to develop their soft skills such as team work, independent learning and communications. Thus, JKKP decided to formalize this event and integrated it into curriculum delivery as early as the first year through The Introduction to Chemical and Biochemical Engineering course beginning at the 2007-2008 academic year. This paper highlights the implementation on Chem-E-Car as part of the learning activities and the impacts on the students in their effort to achieve the learning outcomes. Over that past two academic sessions, the students have shown serious commitment and participation in this activity. The Chem-E-Car competition provides excellent opportunity for students to develop their soft skills.

In this paper, a spectral efficient hybrid wireless optical broadband access network (WOBAN) is proposed and demonstrated based on the transmission of wireless multi-input multi-output orthogonal frequency division multiplexing (MIMO OFDM) signals over wavelength division multiplexing passive optical network (WDM PON). By using radio over fiber (ROF) techniques, the optical fiber is well adapted to propagate multiple wireless services having different carrier frequencies. It is a known fact that multiple wireless signals having the same carrier frequency cannot propagate over a single optical fiber at the same time, such as MIMO signals feeding multiple antennas in fiber wireless (FiWi) system. A novel optical single-sideband frequency translation technique is designed and simulated to solve this problem. This technique allows four pairs of wireless MIMO OFDM signals with the same carrier frequency for each pair to be transmitted over a single optical fiber by using one optical source per wavelength. The crosstalk between the different MIMO channels with the same frequency is eliminated, since each channel is upconverted on specified wavelength with enough channel spacing between them. Also the maximum crosstalk level between the different MIMO channels with different frequencies is very low around −76 dB. The physical layer performance of the proposed WOBAN is analyzed in terms of the bit error rate (BER), error vector magnitude (EVM), and signal-to-noise ratio (SNR). The proposed WOBAN achieves 7.68 Gb/s data rate for 20 km for the optical back-end and 240 Mb/s for the outdoor wireless front-end.

This work involves in transmitting of intermediate frequency (IF) signal over fiber utilizing photonics frequency conversion, which, the main focus is the development of optical front-end receiver. The system uses photodiode and heterojunction bipolar transistor (HBT) to detect and up-convert the received IF modulated optical signal. The photodiode (PD) and HBT are very useful devices for photonics frequency conversion technique with high internal gain and frequency up conversion of optical signal. Through simulation, the optimum device parameters and characteristics were determined. The system was implemented to detect a 0.4 GHz of IF carriers signal and up-converted to 3.4 GHz of radio frequency (RF) signal. The optimum conversion gain that has been obtained from the measurement and simulation were about -11 dB and -8 dB, respectively, at V BE = 0.7 V, P LO = 4 dBm, and -25 dBm of IF optical input power. The system has been practically demonstrated and shown to agree reasonably well with both the theory and simulation. This article also refers to some recent patents on frequency conversion techniq.

A photodefinable polymer of benzocyclobutene (BCB 4024-40) from Dow Chemical™ has been demonstrated as a waveguiding material in a new structure of optical wavelength filter. The filter structure is based on the combination of restricted interference and general interference schemes of multimode interference technique. The filter is capable in optical wavelength filtering particularly for 1550/1310 nm. Because of the photosensitive nature of the polymer, the chemical wet-etching fabrication technique needs to be adopted. For the purpose of laser coupling, a new facet polishing technique has been proposed and it is based on the combination of mechanical and chemical polishing. It is shown that the fabricated device works well with improved crosstalk of −15.7 dB (1310 nm) and −21.8 dB (1550 nm). © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1301–1313, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26781

The hybrid optical–wireless access network (HOWAN) is a favorable architecture for next generation access network. It is an optimal combination of an optical backhaul and a wireless front-end for an efficient access network. In this paper, the HOWAN architecture is designed based on a wavelengths division multiplexing/time division multiplexing passive optical network (WDM/TDM PON) at the optical backhaul and a wireless fidelity (WiFi) technology at the wireless front-end. The HOWAN is proposed that can provide blanket coverage of broadband and flexible connection for end-users. Most of the existing works, based on performance evaluation are concerned on network layer aspects. This paper reports physical layer performance in terms of the bit error rate (BER), eye diagram, and signal-to-noise ratio (SNR) of the communication system. It accommodates 8 wavelength channels with 32 optical network unit/wireless access points (ONU/APs). It is demonstrated that downstream and upstream of 2 Gb/s can be achieved by optical backhaul for each wavelength channel along optical fiber length of 20 km and a data rate of 54 Mb/s per ONU/AP along a 50 m outdoor wireless link.

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.