We report on a hybrid DWDM-TDM A optical access network that provides a route for integrating access and metro net- works into a single all-optical system. The greatest challenge in using DWDM in optical access networks is to precisely align the wavelength of the customer transmitter (Tx) with a DWDM wave- length grid at low cost. Here, this was achieved using novel tunable, external cavity lasers in the optical network units (ONUs) at the customer's end. To further support the upstream link, a 10 Gb/s burst mode receiver (BMRx) was developed and gain-stabilized erbium-doped fiber amplifiers (EDFAs) were used in the network experiments. The experimental results show that 10 Gb/s bit rates can be achieved both in the downstream and upstream (operated in burst mode) direction over a reach of 100 km. Up to 32 50 GHz spaced downstream wavelengths and another 32 50 GHz spaced upstream wavelengths can be supported. A 512 split per wave- length was achieved: the network is then capable of distributing a symmetric 320 Gb/s capacity to 16384 customers. The proposed architecture is a potential candidate for future optical access net- works. Indeed it spreads the cost of the network equipment over a very large customer base, allows for node consolidation and integration of metro and optical access networks into an all-optical system.

We present experimental results on the performance of antenna-integrated photodiodes intended for use as photomixers to provide a tunable broadband source of terahertz (THz) radiation. In a balanced strain-absorber structure, we show that the introduction of strain has proved effective in enhancing the performance at frequencies above 500 GHz. A comparison of strained and unstrained devices confirms this claim. These structures are integrated with a range of antennas, including log periodic and slot-horn types, designed for wideband THz emission. Using the devices as photomixers for the outputs from a DFB laser and an external cavity laser in the 1550 nm telecom window, tunable emission is demonstrated over the range from 100 GHz to 1.8 THz.

We present a hybrid dense wavelength-division-multiplexed time-division multiple access passive optical network (DWDM-TDMA PON) with record performance in terms of reach (135.1 km of which 124 km were field-installed fibers), number of supported optical network units (ONUs-8192) and capacity (symmetric 320 Gb/s). This was done using 32-, 50-GHz-spaced downstream wavelengths and another 32-, 50-GHz-spaced upstream wavelengths, each carrying 10 Gb/s traffic (256 ONUs per wavelength, upstream operated in burst mode). The 10 Gb/s downstream channels were based upon DFB lasers (arranged in a DWDM grid), whose outputs were modulated using a electro-absorption modulator (EAM). The downstream channels were terminated using avalanche photodiodes in the optical networks units (ONUs). Erbium-doped fiber amplifiers (EDFAs) provided the gain to overcome the large fiber and splitting losses. The 10 Gb/s upstream channels were based upon seed carriers (arranged in a DWDM grid) distributed from the service node towards the optical network units (ONUs) located in the user's premises. The ONUs boosted, modulated, and reflected these seed carriers back toward the service node using integrated 10 Gb/s reflective EAM-SOAs (EAM-semiconductor optical amplifier). This seed carrier distribution scheme offers the advantage that all wavelength referencing is done in the well-controlled environment of the service node. The bursty upstream channels were further supported by gain stabilized EDFAs and a 3R 10 Gb/s burst-mode receiver with electronic dispersion compensation. The demonstrated network concept allows integration of metro and optical access networks into a single all-optical system, which has potential for capital and operational expenditure savings for operators.

We report on advanced millimeter-wave (mm-wave) photonic components for broadband radio transmission. We have developed self-pulsating 60-GHz range quantum-dash Fabry-Perot mode-locked laser diodes (MLLD) for passive, i.e., unlocked, photonic mm-wave generation with comparably low-phase noise level of -76 dBc/Hz @ 100-kHz offset from a 58.8-GHz carrier. We further report on high-frequency 1.55-μm waveguide photodiodes (PD) with partially p-doped absorber for broadband operation (f 3dB ~70-110 GHz) and peak output power levels up to +4.5 dBm @ 110 GHz as well as wideband antenna integrated photomixers for operation within 30-300 GHz and peak output power levels of -11 dBm @ 100 GHz and 6-mA photocurrent. We further present compact 60-GHz wireless transmitter and receiver modules for wireless transmission of uncompressed 1080p (2.97 Gb/s) HDTV signals utilizing the developed MLLD and mm-wave PD. Error-free (BER = 10 -9 , 2 31 - 1 PRBS, NRZ) outdoor wireless transmission of 3 Gb/s over 25 m is demonstrated, as well as wireless transmission of uncompressed HDTV signals in the 60-GHz band. Finally, an advanced 60-GHz photonic wireless system offering record data throughputs and spectral efficiencies is presented. For the first time, we demonstrate photonic wireless transmission of data throughputs up to 27.04 Gb/s (EVM 17.6%) using a 16-QAM OFDM modulation format resulting in a spectral efficiency as high as 3.86 b/s/Hz. Wireless experiments were carried out within the regulated 57-64-GHz band in a lab environment with a maximum transmit power of - 1 dBm and 23 dBi gain antennas for a wireless span of 2.5 m. This span can be extended to some 100 m when using high-gain antennas and higher transmit power levels.

We present design and experimental results on novel antenna-integrated edge-coupled photodiodes, examining particularly their suitability as photomixers for broadband terahertz sources. We show that a simple “stub” detector positioned at the edge of the chip can yield promising overall performance when integrated with a number of different planar antennas specifically designed for this configuration. Using a slot-horn antenna connected via a coplanar line, we measure terahertz emission figures of 100 μW over the range 100-500 GHz, with 50 μW available at 750 GHz. We also present a novel planar double-horn antenna and show that with suitable use of terahertz “optics” this offers broadband through-substrate emission from 200 GHz to over 1 THz, with 10 μW terahertz power emitted at 1.004 THz.

The demand for accuracy and precision at the micro–nano level is constantly increasing in the manufacture of high added value products. This requires control and measurement of the surface structure since surface properties at such tiny scales are the dominant functional determinant. Many commercial instruments have been used for surface measurements. However, these devices are almost always operated in an off-line environment, and are not suitable for on-line application. This paper presents a new interferometry system consisting of a chip tuneable laser for future on-line micro–nano scale surface measurements. It is simple, compact and robust as most environmental noise and disturbance can be eliminated without any servo control system due to the near common path configuration and the compact construction. The experimental results show that this system has good performance, and there is scope to improve this if the performance of the laser is enhanced.