Photonic balancing - a scheme where logically opposite pulses derived from the two outputs of a delay-line demodulator
for phase shift keyed (PSK) signals counter-propagate in the saturated regime of a semiconductor optical amplifier
(SOA) - has been proven to enhance the receiver performance, e.g. in terms of decreased optical signal-to-noise-ratio
(OSNR) requirements for a given target bit error ratio (BER). Here, we extend the photonic balancing scheme towards a
new concept for a regenerative amplifier targeted at extending the reach and/or the number of subscribers in passive
optical networks (PON) in order to support major operators' plans to reduce the number of central offices and access
areas by approximately 90%. For a given target BER, we demonstrate experimentally (a) an 8-dB higher post-amplifier
loss tolerance, (b) an extended feeder line length (75 km) combined with high splitting ratio (10 layers) for a preamplified
version, and (c) high input power variation tolerance (> 30 dB burst-to-burst) in upstream direction as needed
for highly asymmetric tree structures.
We present an optical receiver for RZ-DPSK signals that use photonic balancing. Photonic balancing is achieved through
pulse counter-propagation and collision in a saturated SOA. We explain the principles of photonic balancing and show
how it can lead to an improvement in RZ-DPSK detection by 3 dB, similar to electrical balancing. We also show how
this scheme can be used as a Mamyshev-type regenerator.
In this paper, we propose and experimentally demonstrate a pressure sensor based on birefringent single mode
fiber FP cavity using optical heterodyne. The proof of concept device consists of a light source, a polarizer controller,
a modulator, a RF generator, a single mode fiber Fabry-Perot cavity, a strain inspector, an erbium doped fiber amplifier,
a filter, a polarizer, an optical spectrum analyzer, and a digital communication analyzer. The dynamic range of the
proposed sensor is explored. The results demonstrate the new concept of fiber pressure sensors and the technical
feasibility for pressure measurements.
Sophisticated modulation formats like phase shift keying (PSK) as discussed for high-speed fiber-optic transmission systems operating at 40 Gbit/s and beyond, cause new challenges for clock recovery. Whereas conventional return-to-zero on-off keyed (RZ-OOK) modulated signals provide proper clock tones which can be used to recover the clock signal, the additional phase modulation (RZ-PSK) changes the spectral composition of the signal and weakens or suppresses the clock tones. This effect is bit pattern dependent as can be seen from a simple example: If all the pulses in an RZ-PSK signal are in phase, the result is equivalent to an ordinary RZ on-off-keying (OOK) signal with a strong carrier and clock tones. If the pulses in a sequence oscillate in phase by &pgr;, the result is equivalent to the well-known carrier-suppressed return-to-zero signal (CS-RZ) where the carrier is suppressed and where clock tones are differently spaced compared to RZ-OOK. In this paper we present results of the simulation of the different cases taking into account realistic bit sequences and analyze the results with special emphasis on the influence the effect has on clock recovery.
Future transparent networks require optical regeneration. The regeneration process of amplitude-modulated signals
consists of three key stages: re-amplification, re-shaping, and re-timing. In this Paper we briefly review various optical
clock recovery methods and propose a polarization insensitive low-cost scheme capable of resolving timing information
simultaneously for multiple wavelength channels. We also discuss the prospects of low-cost volume production with
integrated optics and especially with Si-photonics.