This paper reviews recent progress on high-speed technologies for optical transmission systems in the IP and FTTH era. First, we describe our latest research results of 160 Gbit/s optical time-division multiplexing and demultiplexing experiments. The all-optical time-division multiplexer is realized as a hybrid integrated device consisting of planar lightwave circuits (PLC's) and highly-nonlinear periodically-poled lithium niobate (PPLN) waveguides while the demultiplexer is realized as a hybrid integrated device consisting of PLC's and semiconductor optical amplifiers. A new type of all-optical switch that uses a photonic crystal nanocavity and an all-optical flip-flop circuit that is composed of two-port resonant-tunneling filters based on a two dimensional photonic crystal slab with triangular air-hole lattice are shown. Finally, the possibility of over 100 Gbit/s all-optical signal processing is discussed for high-speed optical transmission systems.
KEYWORDS: Clocks, Optical networks, Eye, Signal to noise ratio, Signal detection, Modulators, Distortion, Error analysis, Picosecond phenomena, Signal processing
Optical signal quality monitoring is an important function for optical transport networks and future all-optical networks. To monitor the optical signal-to-noise ratio and/or waveform distortion transparently with respect to the signal format, data format, and signal bit rate, we introduce an optical signal quality monitoring method that uses asynchronous sampling, which is a sampling technique that does not use timing extraction. The use of high-speed asynchronous sampling and the adjustment of the sampling rate enable simple open eye-diagram monitoring and evaluation of a fixed-timing Q-factor (Qt) at the maximum eye opening timing phase. This method was experimentally verified using an optical signal quality monitoring circuit, and obtained a good relationship between the measured Qt and Q (which is a Q-factor calculated from the bit error rate (BER)). Moreover, we also introduce an average Q-factor (Qavg) evaluation method, which measures the Qavg value from an asynchronous eye-diagram (timing drifted eye-diagram). This method is useful when the sampling rate is low or when adjusting the sampling rate is difficult.
Photonic crystal fibers (PCFs) and photonic bandgap fibers (PBFs) for high performance systems and devices are reviewed. A PCF has an array of air holes surrounding a silica core region. The PCF has special characteristics compared with conventional single mode fibers. Theoretical analyses and measurements show that the zero dispersion wavelength of PCF is shorter than 1280 nm that is suitable for dispersion compensation at 1550 nm. PCFs with zero dispersion in the 1550 nm region were recently proposed. Another noteworthy characteristic of PCFs is their strong
birefringence, which is induced by the size and arrangement of the air holes. A theoretical analysis and experiments showed high birefringence, three times larger than that of conventional polarization maintaining fibers. Therefore, optical components with better polarization maintaining characteristics are expected. The new topic is PBFs that have hollow core and a lattice in the surrounding region to form a photonic band gap. They are expected to realize low-loss, low-dispersion, and low nonlinerity fiber because the core is air. Recently we proposed a new type PBF to aim at wide bandgap opening by using superlattice structure. This paper describes the characteristics of dispersion controlled PCFs, polarization maintaining PCFs, and the band structure and experimental results of the new PBF. The potential of PCFs and PBFs will be discussed with reference to the next generation high performance networks.
Photonic crystal fibers (PCFs) confine light by the regularly aligned cladding air-holes. PCFs can produce large birefringence of >10-3 by asymmetrical structures. Since the polarization mode in the slow axis is hard to couple to the fast axis mode due to the large birefringence, such PCFs can be used as polarization maintaining fibers. To induce such anisotropy, some hole patterns can be considered. In this paper, the structures of polarization maintaining PCFs, two defects type and enlarged type are described. In 100 m fiber, the extinction ratio better than -20 dB and -30 dB were obtained for former and latter type PCF, respectively. We have also examined the cross-talk degradation by the bending distortion. In the bending diameter of 10 mm, the cross-talk degradation was no larger than the measurement accuracy of 0.2 dB in such polarization maintaining photonic crystal fibers, but the 20 dB degradation was observed in the PANDA fiber, which was the conventional polarization maintaining fiber.
Recent progress on holey fibers is reviewed aiming at their application to optical communications. A holey fiber has an array ofair holes surrounding the silica core region. Light is confined to the core by the refractive index difference between the core and the cladding ofthe array of air holes. Holey fibers have special characteristics compared with conventional single mode fibers. One is that the zero dispersion wavelength is shifted to less than 1300 nm and therefore, high-speed transmission at the short wavelength region is possible. Another characteristic is that strong birefringence can be established by designing the size or arrangement of the air holes and is expected to realize a polarization maintaining fiber with high birefringence on the order of 1 x iO. This talk will describe the technology needed to design and fabricate holey fibers. Recent experimental results of a holey fiber with zero dispersion wavelength of 8 1 0 nm and a polarization-maintaining lowloss (1.3 dB/km) holey fiber are shown. The possibility oftheir application to optical communications is discussed.
As the demand for optical fiber communications bandwidth grows, the implementation of signal processing functions using all-optical techniques becomes increasingly attractive. In recent years, a number of methods have been used to perform functions such as wavelength conversion for WDM systems, gated mixing for TDM multiplexing and demultiplexing, spectral inversion for dispersion compensation, and all-optical switching. Three-wave mixing in c(2) media is an attractive approach, presenting a combination of low pump power, wide bandwidth, and negligible degradation of signal to noise ratio. In this paper, we describe optical frequency mixers implemented using annealed proton exchanged waveguides in periodically poled lithium niobate. These devices have been used in a variety of system experiments. We present several WDM demonstrations, including wavelength conversion, dispersion compensation by mid-span spectral inversion, and compensation of Kerr nonlinearities. We also discuss TDM demonstrations such as efficient all-optical gating and multiplexing/demultiplexing of high bit-rate data streams.
As the demand for optical fiber communications bandwidth grows, the implementation of signal processing functions using all-optical techniques becomes increasingly attractive. In recent years, a number of methods have been used to perform functions such as wavelength conversion for WDM systems, gated mixing for TDM multiplexing and demultiplexing, spectral inversion for dispersion compensation, and all-optical switching. Three-wave mixing in (chi) (2) media is an attractive approach, presenting a combination of low pump power, wide bandwidth, and negligible degradation of signal to noise ratio. In this paper, we describe optical frequency mixers implemented using annealed proton exchanged waveguides in periodically poled lithium niobate. These devices have been used in a variety of system experiments. We present several WDM demonstrations, including wavelength conversion, dispersion compensation by mid-span spectral inversion, and compensation of Kerr nonlinearities. We also discuss TDM demonstrations such as efficient all-optical gating and multiplexing/demultiplexing of high bit-rate data streams.
Recent progress in ultrafast all-optical ThM transmission technologies is reviewed including optical short pulse generation, time-division multiplexing/demuitiplexing and timing extraction. A 400 Gbit/s TDM transmission experiment and a 120 Gbit/s prototype are shown and the possibility of Thitls TDM is discussed.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.