Frequently Asked Questions

COMPANY

Q: What is LD4B?

A: LD4B is a photonics company specializing in fiber-coupling of semiconductor laser diodes, superluminescent diodes (SLDs), and photodiodes. We design and manufacture advanced fiber-coupled laser and detector modules that deliver high performance and reliability.

Q: Where are LD4B products used?

A: LD4B products are widely used in microwave photonics, optical time-domain reflectometry, telecommunications, datacom, fiber sensing, medical equipment, and scientific research.

Q: What does LD4B mean?

A: LD4B stands for “Laser Diode for Business.” The name reflects our focus on providing high-quality optoelectronic solutions. While our roots are in laser diodes, we also manufacture superluminescent diodes (SLDs) and photodiodes, all with advanced fiber-coupling technology.

Q: Who works at LD4B?

A: LD4B is driven by a team of engineers and scientists passionate about photonics. Our expertise covers precise optical fiber alignment and the manufacturing of reliable fiber-coupled laser diodes, superluminescent diodes (SLDs), and photodiodes.

Q: Where is LD4B located?

A: LD4B is located in Warsaw, Poland. Our facility at ul. Konstruktorska 6, lokal 108, 02-673 Warsaw manufactures fiber-coupled laser diodes, superluminescent diodes (SLDs), and photodiodes for customers worldwide.

Q: Is LD4B a manufacturer?

A: Yes, LD4B is a manufacturer specializing in alignment, and packaging; however, we do not produce wafers or grow semiconductor chips.

LASER DIODES

Q: What are fiber-coupled laser diodes?

A: Fiber-coupled laser diodes are semiconductor lasers that emit coherent light directly into an optical fiber. They simplify the integration of lasers into optoelectronic systems, providing precise, stable, and efficient light delivery for applications in telecommunications, sensing, and industrial laser systems.

Q: What laser diodes does LD4B offer?

A: LD4B offers fiber-coupled laser diodes with wavelengths from 500 nm to 1650 nm. Most of our diodes are coupled to single-mode or polarization-maintaining fibers, delivering tens of milliwatts of optical power from the fiber for high-precision applications in industrial photonics.

Q: Does LD4B offer telecom laser diodes?

A: Yes, LD4B offers telecom-grade laser diodes suitable for analog and digital optical communication. Our products include DFB laser diodes capable of data rates up to 2.5 Gbps or 10 Gbps, optimized for high-speed fiber-optic networks.

Q: What is the difference between Fabry-Perot and DFB laser diodes?

A: A DFB (Distributed Feedback) laser diode is a single-frequency laser with a narrow linewidth and a single spectral peak. A Fabry-Perot (FP) laser diode has no frequency-selective element, producing a wider spectrum with multiple modes.

Q: What is the linewidth of a DFB laser diode?

A: The linewidth of a DFB laser diode is typically less than 1 MHz, making it too narrow to measure with standard grating-based optical spectrum analyzers. Specialized techniques, such as the self-delayed heterodyne method, are required for accurate linewidth measurement.

Q: What is the difference between single-mode and multimode laser diodes?

A: Single-mode laser diodes produce a narrow Gaussian beam with only one transverse mode, supporting high spatial coherence and precision. In contrast, multimode laser diodes emit multiple transverse modes, resulting in a wider, less focused beam with higher output power but lower spatial quality.

Q: What is the difference between single-mode and multimode fiber-coupled laser diodes?

A: Single-mode fiber supports only a single transverse mode with a small core, enabling long-distance, high-bandwidth transmission. Multimode fiber supports multiple light modes with a larger core, suitable for shorter distances. Single-mode laser diodes can couple to both fiber types, but multimode laser diodes only couple efficiently with multimode fiber.

SUPERLUMINESCENT DIODES

Q: What are superluminescent diodes (SLDs)?

A: Superluminescent diodes (SLDs) are broadband, incoherent light sources. Their emission spectrum is similar to LEDs, but they are more directional and can be efficiently coupled into optical fibers, making them ideal for fiber-optic sensing, imaging, and high-precision photonics applications.

Q: What superluminescent diodes does LD4B offer?

A: LD4B offers fiber-coupled superluminescent diodes (SLDs) with wavelengths ranging from 670 nm to 1550 nm and optical powers of a few milliwatts.

PHOTODIODES

Q: What are photodiodes?

A: Photodiodes are optoelectronic devices that convert light into electrical current. They are widely used in fiber-optic communication, sensing, and measurement systems for high-speed and precise optical detection.

Q: What photodiodes does LD4B offer?

A: LD4B offers PIN photodiodes, avalanche photodiodes (APDs), and photodiodes with integrated transimpedance amplifiers (TIA). These photodiodes are designed for high-speed optical detection in microwave photonics, OTDR, digital communication, fiber-optic sensing and security applications.

TECHNOLOGY

Q: Which optical fibers does LD4B couple light to?

A: LD4B specializes in coupling light to single-mode and polarization-maintaining fibers with core diameters from 3 to 10 µm. We also provide fiber coupling for multimode fibers with core sizes of 50 µm, 62.5 µm, and 105 µm if it is required for specific application.

Q: What packages does LD4B offer?

A: LD4B offers coaxial packages without thermal stabilization and 14-pin DIL and BTF packages with thermal stabilization (TEC and thermistor). Compact coaxial packages suit low-heat modules like photodiodes or laser diodes in low duty cycle pulse mode. For CW laser diodes or SLDs, coaxial packages with brackets allow heat sink attachment. See more here

Q: Does LD4B offer controllers for laser diodes?

A: LD4B does not manufacture laser diode controllers directly but offers controllers from trusted partner companies. Customers can order these controllers together with LD4B fiber-coupled laser diodes for seamless compatibility and integration.

Q: Are there drawings and 3D models of LD4B modules available?

A: Yes, LD4B datasheet PDFs include active buttons with hyperlinks to detailed module drawings in PDF format and 3D models in STEP files, enabling easy access to mechanical and dimensional data for precise integration and design.

Q: Which technologies does LD4B use?

A: At LD4B, we specialize in advanced fiber-lensing and active alignment techniques to achieve highly efficient fiber coupling of laser diodes, superluminescent diodes (SLDs), and photodiodes. Our proprietary methods ensure low-loss light delivery, excellent stability, and reliable performance in demanding optical systems.

Q: What is special about LD4B’s laser diode pigtailing technology?

A: LD4B employs two specialized pigtailing technologies tailored for different application priorities. The first technology achieves higher coupling efficiency with a typical variation of about 0.5 dB in the telecom wavelength range due to temperature changes. The second technology prioritizes exceptional stability of the coupling against temperature fluctuations, offering highly consistent performance but with slightly lower coupling efficiency. These options enable customers to choose fiber coupling solutions optimized either for maximum optical power or for superior thermal stability, depending on their system requirements.

Q: What is special about LD4B’s photodiode pigtailing technology?

A: LD4B utilizes two distinct photodiode pigtailing technologies to optimize performance for different application needs. One technology minimizes back-reflection, which is crucial for reducing interference, though it may introduce some polarization-dependent loss (PDL). The second technology employs refractive index matching between the optical fiber and photodiode to effectively eliminate Fresnel reflections at the fiber-air interface, thereby increasing responsivity and reducing PDL. This approach enhances overall detector sensitivity and signal quality, making it ideal for high-precision optical measurement systems.

Q: How does LD4B test the reliability of pigtailed modules?

A: LD4B focuses on the reliability of fiber alignment and packaging in our assemblies. We rigorously test our modules following the Telcordia GR-468 CORE standard, a leading industry benchmark for optical component reliability. Our comprehensive testing includes mechanical shock and vibration, multiple thermal cycling, high and low temperature storage, thermal shocks, fiber integrity, and leak tests. These tests ensure our modules deliver stable, long-term performance in demanding industrial environments.

Q: Under what conditions does LD4B assemble pigtailed modules?

A: LD4B assembles pigtailed modules in controlled clean environment within laminar flow hoods to maintain high standards of cleanliness and contamination control. Strict precautions against electrostatic discharge (ESD) are implemented throughout the process. Additionally, modules are backfilled with dry nitrogen to protect internal components and enhance reliability. Each assembled module undergoes thorough electrical and optical testing to ensure optimal performance before delivery.

Q: How are LD4B modules packed?

A: Each LD4B module is carefully packed to ensure protection and reliability during shipping and handling. Modules are placed in vacuum-sealed, ESD-safe bags to prevent static discharge and contamination. They are further cushioned with ESD-safe bubble foil and securely enclosed in sturdy carton boxes to safeguard against mechanical damage. This packaging approach preserves the modules' integrity until they reach the customer.

ORDERING

Q: How can I place an order with LD4B?

A: To place an order, please send your request via email or use the contact form on our website. We will respond promptly—typically within one business day—to discuss your specifications and offer the best solution tailored to your needs. We welcome open communication to understand your requirements and help find the optimal fiber-coupled module for your application.

Q: Does LD4B keep ready modules in stock?

A: Due to the wide variety of module configurations—including different package types, fiber types and lengths, and connector options—LD4B does not maintain ready-made modules in stock. Instead, we assemble each module promptly after receiving an order. Typical lead times for small orders are approximately 2 weeks for coaxial modules and 3 weeks for DIL-14-pin or BTF-14-pin modules. This approach ensures customized solutions tailored to each customer’s exact specifications.

Q: What are the payment terms at LD4B?

A: For first-time customers, LD4B may require prepayment to establish trust and ensure smooth processing. For subsequent orders, we typically offer standard NET30 payment terms, meaning payment is due within 30 days from the invoice date. We aim to provide transparent and flexible payment conditions to support a strong partnership with our clients.

Q: Is it possible to pay by card at LD4B?

A: While LD4B prefers direct bank wire transfers for payments, we understand that convenience is important. Therefore, if payment by card is more convenient for the customer, we can also offer this option upon request. Our goal is to provide flexible payment methods to best suit our clients' needs.

Q: Does LD4B have distributors in other countries

A: LD4B sells directly worldwide, but we also have distributors in some countries (for example, USA, India, South Korea, Japan). Contact us for your local option. 

Q: How does LD4B ship its products?

A: LD4B typically ships products using reliable express delivery services such as DHL, FedEx, and UPS. These trusted carriers ensure fast and secure delivery worldwide, with full tracking capabilities to keep customers informed throughout the shipping process.

Q: What are the warranty terms? 

A: LD4B standard warranty covers our modules for one year from the date of delivery or up to 5,000 operating hours—whichever comes first. The warranty protects against manufacturing defects and intrinsic material faults, provided the product has not been altered, incorrectly installed, misused, or repaired by the user.

Q: What happens if a module fails?

A: In case of failure, the customer must notify LD4B in writing within one week of discovering the fault, providing detailed information. The faulty product must be returned before the warranty expires. LD4B will perform a failure analysis free of charge and will repair or replace any product that fails under warranty conditions. Shipping costs for returning products are not covered by the warranty. After the warranty period, failure root cause analysis is still available at no cost, but shipping expenses remain the responsibility of the customer.

Q: Does LD4B provide test datasheets?

A: Yes, absolutely. Every LD4B module undergoes comprehensive electrical and optical testing, and a detailed test datasheet (TDS) is generated for each unit. The TDS is sent to customers via email, and a printed copy of the general datasheet is included in the shipment for reference. This ensures customers receive full transparency on their module’s performance and specifications.