Detailed investigation on reliability of wavelength-monitor-integrated fixed and tunable DFB laser diode modules

Free-Space Laser Communication and Atmospheric Propagation XXVI

Carney

Fitzgerald

et al. 2014

We describe a flexible high-sensitivity laser communication transceiver design that can significantly benefit performance and cost of NASA's satellite-based Laser Communications Relay Demonstration. Optical communications using differential phase shift keying, widely deployed for use in long-haul fiber-optic networks, is well known for its superior sensitivity and link performance over on-off keying, while maintaining a relatively straightforward design. However, unlike fiber-optic links, free-space applications often require operation over a wide dynamic range of power due to variations in link distance and channel conditions, which can include rapid kHz-class fading when operating through the turbulent atmosphere. Here we discuss the implementation of a robust, near-quantum-limited multi-rate DPSK transceiver, co-located transmitter and receiver subsystems that can operate efficiently over the highly-variable freespace channel. Key performance features will be presented on the master oscillator power amplifier (MOPA) based TX, including a wavelength-stabilized master laser, high-extinction-ratio burst-mode modulator, and 0.5 W single polarization power amplifier, as well as low-noise optically preamplified DSPK receiver and built-in test capabilities.

Section: Laser Wavelength Controlmentioning

confidence: 99%

Multi-rate DPSK optical transceivers for free-space applications

Free-Space Laser Communication and Atmospheric Propagation XXVI

Carney

Fitzgerald

et al. 2014

“…For Telcordia-qualified laser diodes [4,5], the mean-time-to-failure (MTTF) can exceed 100 years (∼1 × 10 6 h) [231]. A practical feature of semiconductor lasers is that the output power can be directly modulated, at speeds approaching the relaxation oscillation frequency [232,233], f RO , which is given by…”

Section: Direct Modulation and Semiconductor Laser Sourcesmentioning

confidence: 99%

“…The only additional cost for tunability becomes the additional DACs and the feedback mechanism. In addition to using calibrated current and temperature to control DFB laser wavelength, integrated etalon-based wavelength monitors are commercially available with Telcordia qualification [5], providing compact, reliable, locally-resident sub-GHz resolution feedback that can be used to align the laser wavelength over a 20+ year lifetime [231,265]. In some cases, the feedback information on laser wavelength (and power) can be remotely located, for instance at the receive terminal, and periodically be communicated back to the laser control via low-bandwidth back channel [266][267][268] (see section 5.2.2).…”

Section: Laser Wavelength Controlmentioning

confidence: 99%

“…The pilot signal, which could be generated by a low-power DFB laser, is injected into the DI through an optical tap in the reverse direction. As discussed in section 3.3 and earlier in this section, the pilot wavelength λ p can be calibrated via temperature and current settings with a (short term) stability <∼30 MHz [135], or through other methods, such as a feedback from a built in temperature controlled etalon [231] or an external wavelength reference such as a wavemeter, with sub-GHz long-term stability.…”

Section: Interferometer Stabilizationmentioning

confidence: 99%

See 1 more Smart Citation

Laser communication transmitter and receiver design

2007

J Optic Comm Rep

116

Free-space laser communication systems have the potential to provide flexible, high-speed connectivity suitable for long-haul intersatellite and deep-space links. For these applications, power-efficient transmitter and receiver designs are essential for cost-effective implementation. State-of-the-art designs can leverage many of the recent advances in optical communication technologies that have led to global wideband fiber-optic networks with multiple Tbit/s capacities. While spectral efficiency has long been a key design parameter in the telecommunications industry, the many THz of excess channel bandwidth in the optical regime can be used to improve receiver sensitivities where photon efficiency is a design driver. Furthermore, the combination of excess bandwidth and average-power-limited optical transmitters has led to a new paradigm in transmitter and receiver design that can extend optimized performance of a single receiver to accommodate multiple data rates. This paper discusses state-of-the-art optical transmitter and receiver designs that are particularly well suited for average-power-limited photon-starved links where channel bandwidth is readily available. For comparison, relatively simple direct-detection systems used in short terrestrial or fiber optic links are discussed, but emphasis is placed on mature high-performance photon-efficient systems and commercially available technologies suitable for operation in space. The fundamental characteristics of optical sources, modulators, amplifiers, detectors, and associated noise sources are reviewed along with some of the unique properties that distinguish laser communication systems and components from their RF counterparts. Also addressed is the interplay between modulation format, transmitter waveform, and receiver design, as well as practical tradeoffs and implementation considerations that arise from using various technologies.

“…Thus, for 40 Gbit/s channels received with a 40 GHz interferometer, each channel would need to be within ±1.6 GHz of the target interferometer fringe in order to bound the SNR penalty to less than 0.5 dB (when used with FEC). Reliable sub-GHz control can be readily achieved via DFB laser temperature and current control alone [16] or in combination with (integrated) λ-monitoring feedback [20].…”

Section: Fig 1 (A)mentioning

confidence: 99%

High-Sensitivity Demodulation of Multiple-Data-Rate WDM-DPSK Signals using a Single Interferometer

OFC/NFOEC 2007 - 2007 Conference on Optical Fiber Communication and the National Fiber Optic Engineers Conference

Stevens

Carney

2007

We demonstrate simultaneous reception of multiple-rate wavelength-division-multiplexed optical-DPSK signals using a single interferometer. The demodulation approach provides rate-flexibility and scalability, enabling penalty-free performance and compliance with existing channel-rate and channel-spacing standards. 1Introduction Optical differential-phase-shift-keying (DPSK) modulation has received considerable attention by the free-space optical (FSO) communications community and the telecom industry for its increased sensitivity over commonly used on-off-keying [1-6], and reduced peak-to-average power ratio which mitigates nonlinear effects in fiber-optic applications. These benefits have led to many Tbit/s long-haul fiber-optic experiments using hundreds of WDM-DPSK channels [7-10]. The advantages of DPSK come at the expense of increased complexity, requiring a phase modulator in the transmitter (TX), and an optical delay-line interferometer (DI) and balanced detection in the receiver (RX) to derive maximum benefit. Of these elements, the DI is the most technically challenging and the least mature. For good performance, the arms of the DI must be precisely fabricated to within a small fraction of a bit-period, and they must be stable to a small fraction of a wavelength, requiring careful thermo-mechanical packaging and/or stabilization electronics [11][12][13][14], adding to size, weight, power, and cost.Miyamoto and coauthors [15] demonstrated interferometer sharing by converting 42.7 Gbit/s WDM-DPSK channels to WDM-duobinary channels on the 100 GHz ITU grid using a 50 GHz free-spectral-range (FSR) DI. Their innovative DPSK RX has advantages in dispersion-limited fiber links, but has inherent sensitivity penalties of 3 dB due to single-ended DPSK reception and an additional penalty due to the rate-to-FSR mismatch. While their simplified approach enables ITU compatibility, the ~14% mismatch leads to a waveform-dependent penalty of ~1.2 dB for 33% RZ pulse-shapes, further reducing the sensitivity benefit of DPSK [16]. To avoid mismatch penalty, the interferometer delay (τ d = 1/FSR) must be an integer multiple n of the bit-period τ bit , i.e., τ d = nτ bit (see e.g., [17]). Here, we use this relation and the DI's periodic transfer function to demonstrate simultaneous demodulation of 2.5 Gbit/s and 5 Gbit/s WDM-DPSK signals using a single DI. This technique can be scaled to higher rates and channel count, and operate within existing standards without waveform-dependent penalties. Description of the multi-rate multi-channel DPSK approachPenalty-free multi-channel DPSK reception can be achieved by leveraging the DI's periodic transfer function (Fig. 1a), and constraining the received wavelength spacing (Δν ch ), which enables simultaneous demodulation of all channels (λ's). WDM channel separation is achieved via optical demultiplexing after the DI [15,18,19] (Fig. 1b). dB Normalized Frequency Offset, Δf/FSR cos 2 () sin 2 ()