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Lightwave Technology, Journal of

Issue 1 • Date February 1984

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Displaying Results 1 - 15 of 15
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
  • A 100-km-long single-mode optical-fiber fault location

    Page(s): 1 - 6
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    A Raman OTDR (ROTDR) fault location for a 100-km-long single-mode optical fiber has been tested. A Ge p-i-n photodiode cooled by liquid nitrogen has been used as a backscattered light receiver. The signal-to-noise ration (SNR) improvement of the cooled Ge p-i-n photodiode from a Ge avalanche photodiode (Ge APD), which operates at room temperature, is 14 dB. Spectral Stokes light power distributions, which have been emitted from a long single-mode fiber, have been measured to estimate the maximum locatable length for a single-mode fiber. It has been shown, from the measurements and calculations, that a 100- km-long and a 30-dB total attenuation at a 1.55-μm wavelength single-mode fiber fault location can be achieved with the aid of an averaging technique. On the basis of these results, a 102-km-long single-mode fiber fault location experiment has been successfully carried out. View full abstract»

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  • Direct gigabit modulation of injection lasers - Structure-dependent speed limitations

    Page(s): 40 - 43
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    Samples of a large variety of quaternary 1.3- and 1.5-μm injection lasers were directly modulated at bit rates up to 2 Gbit/s using a drive circuit known to have a flat response up to speeds more than twice this high. The resulting optical signals were detected and analyzed for eye degradation and bit error rates. It was found that some lasers were capable of modulation at rates exceeding 2 Gbit/s without degradation while others exhibited significant eye closure at bit rates as low as 300 Mbit/s. A clear correlation was found between high-speed capability and the absence of a current blocking junction. That is, the lasers capable of the fastest modulation were of the simplest geometries: ridge guide and oxide stripe. Buried heterostructure (BH) and buried crescent (BC) lasers both showed significant speed limitations. The modulation bandwidths of the various lasers were also investigated using small-signal sinusoidal modulation and the measured half-power bandwidths were consistent with the large-signal modulation results. The shape of typical modulation transfer characteristics is consistent with a simpleRCrolloff withRCproducts of ≳ 400 ps for buried crescent lasers, ∼ 150 ps for buried heterostructure lasers, and < 60 ps for ridge guide lasers. These results apply also to samples which had been processed to form cleaved-coupled-cavity (C3) lasers for mode stabilization. View full abstract»

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  • Active spectral stabilization of cleaved-coupled-cavity (C3) lasers

    Page(s): 49 - 51
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    A stabilization technique which will maintain a cleaved-coupled-cavity (C3) laser in single-mode operation over a wide current and temperature range is proposed and demonstrated. View full abstract»

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  • Optical cascade star network - A new configuration for a passive distribution system with optical collision detection capability

    Page(s): 61 - 66
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    A new fiber-optic passive network configuration with novel star couplers is reported. The new optical network configuration, an Optical Cascade Star Network, optimizes contradictory requirements for network system size and cable cost, and matches the actual layout in offices or factories. The star coupler is novel in that the optical signal does not return to the source terminals. This feature enables cascade connection of star networks, the use of simple repeaters for system extension, and the easy support of carrier sense multiple access with collision detection (CSMA/CD) bus access procedure. Experimental results obtained from novel star couplers, optical transceivers with (CSMA/CD) bus compatibility, and a total network system are also discussed. View full abstract»

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  • [Back cover]

    Page(s): c4
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    Freely Available from IEEE
  • Etched-wall bent-guide structure for integrated optics in the III-V semiconductors

    Page(s): 31 - 34
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    Bent-guide structures will undoubtedly play an important role in increasing packing density in future integrated optical circuits. A method for forming bends in waveguides in III-V semiconductors by reflection off an etched vertical wall is proposed for providing wave-guiding through 90° with negligible loss. View full abstract»

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  • Low-loss polarization-independent electrooptical switches at λ = 1.3µm

    Page(s): 51 - 55
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    Polarization-independent single-mode optical cross points with low loss have been fabricated forlambda = 1.3-mum wavelength. Waveguide design, coupling strength equalization for the two polarizations, fabrication tolerances, and the performance of several Ti:LiNbO3directional-coupler switches are presented. Two 2 × 2 switches have been made with fiber pigtails. The switches have an insertion loss of ∼3- andsim-14-dB crosstalk isolation with a 70-V operating voltage. A 4 × 3 switch had similar performance but higher insertion loss. View full abstract»

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  • Design and performance of tuned fiber coil isolators

    Page(s): 56 - 60
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    Optical isolators using coiled single-mode fibers with controlled birefringence have been thoroughly analyzed and tested experimentally. Isolation ratios as high as 44.5 dB with insertion losses (excluding coupling and polarizer losses) of 0.3 to 0.4 dB have been obtained at 633 nm. Analysis indicates that these devices will have >20-dB isolation over a spectral range of 2.5 nm or a temperature range of 36°C. View full abstract»

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  • Statistical measurements as a way to study mode partition in injection lasers

    Page(s): 44 - 48
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    We have demonstrated a statistical measurement technique to characterize the mode partition in injection lasers. In the steady state small nonlasing side modes have distributions similar to that of a narrow-band Gaussian noise. There is a certain probability that they carry a significant portion of the total output. For example, if a side mode of a TJS (AlGa)As laser contains on the average 1.6 percent of the total output power, there is a probability of 10-6, that it carries 30 percent of the total output. Distributions of main modes of a multimode laser can be matched by beta distributions with properly selected parameters. In addition to dc conditions, this technique has also been used to study the transient behavior of injection lasers. The dominant mode has been shown to start from a noise distribution. View full abstract»

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  • Thermal characteristics of jacketed optical fibers with initial imperfection

    Page(s): 18 - 24
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    Thermal characteristics of optical loss and fiber strain in jacketed single-mode optical fibers with initial fiber axis deformation have been examined theoretically and experimentally. Fiber axis deformation due to temperature change is theoretically analyzed by applying buckling theory for a bar on an elastic foundation. Optical loss increase and fiber strain are measured for two kinds of fibers which have different initial fiber axis deformation. Experimental results approximately coincide with values calculated from the theory. It is clarified from these results that the fiber strain due to temperature change is smaller and loss increase at low temperatures is larger for the fiber with larger initial axis deformation. A design method for jacketed single-mode optical fibers to prevent loss increase at low temperatures is given. View full abstract»

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  • Fusion mass-splices for optical fibers using high-frequency discharge

    Page(s): 25 - 31
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    This report describes a high-frequency discharge massheating technique and a fiber aligning mechanism for fusion mass-splicing of silica fibers, and a reinforcement technique for the spliced fibers. Splice loss, operation time, and loss stability of reinforced mass-splices were evaluated by using fiber ribbon units comprising five graded-index fibers with 50-μm core and 125-μm outer diameters. They proved the excellence of the method. View full abstract»

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  • Gain-bandwidth-limited response in long-wavelength avalanche photodiodes

    Page(s): 34 - 39
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    The gain-bandwidth(GB)-limited response of In0.53Ga0.47As/ InP heterostructure avalanche photodiodes (APD's) and related devices used in long-wavelength digital optical receivers is calculated. We find that these diodes, as currently designed, are useful at bit ratesB lsim 2Gbit/s when employed in conjunction with high-sensitivity optical receivers. Response at higher bit rates may be obtained depending on the details of device design. On the other hand, use of poor-quality receivers that require moderate-to-high values of optimum gain can significantly degrade the performance of heterostructure APD's at high bit rates due to GB limitations. We also show that APD receiver bandwidth can be expressed in terms of the sensitivity obtained using the receiver in conjunction with a p-i-n photodiode. It is found that the response speed of optimized receivers is lowest for an APD effective ionization rate ratio ofk = 0.5. View full abstract»

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  • Carrier-induced phase noise in angle-modulated optical-fiber systems

    Page(s): 6 - 10
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    Phase noise in angle-modulated optical-fiber communication systems arising from optical power fluctuations is analyzed. The nonlinear refractive index of silica is the physical mechanism which converts power fluctuations into phase fluctuations. The effects of self-phase modulation (an optical wave acting on itself) and cross-phase modulation in wavelength-division multiplexed (WDM) systems (one optical wave modulating a channel at a different wavelength) have been calculated. The phase noise generated in single-channel systems is negligible for laser fluctuations less than 1-mW rms. In WDM systems containing as few as four channels the phase noise exceeds tolerable levels (0.15 rad) for power fluctuation of 1 mW in each channel. View full abstract»

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  • Evaluation of modal noise in multimode fiber-optic systems

    Page(s): 11 - 18
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    Modal noise at fiber connecting points is studied theoretically and experimentally. Simple formulas for calculating modal-noise power, noise bandwidth, and nonlinear distortions are obtained by introducing a visibility concept. Modal noise for multimode operating LD is also analyzed. These theoretical results are applied to high-bit-rate digital systems and analog systems using direct IM. Then, it is shown that a 3-dB connection loss limits effective signal-to-noise ratio (SNR) to 22 dB in high-bit-rate digital systems, and that in analog systems, the SNR is improved more than 20 dB by using a superimposed pulse modulation with a frequency that is 100 times the baseband signal bandwidth. View full abstract»

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Aims & Scope

The Journal of Lightwave Technology contains articles on current research, applications and methods used in lightwave technology and fiber optics.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Peter J. Winzer
Alcatel-Lucent Bell Labs