Rack-Mounted Optical Fiber Splitter For FTTH Networks With Uniform Fiber Distribution

Optical Fiber Splitter is a core passive component in optical communication networks, and its parameter characteristics directly determine the efficiency and stability of optical signal distribution. The following is a detailed analysis from the dimensions of technical parameters, manufacturing processes, application scenarios, and industry standards.

I. Analysis of Core Optical Parameters

1. Insertion Loss

· Definition: The power attenuation of an optical signal at the output end relative to the input end after passing through a splitter, calculated as /(A_i = -10/lg(P_{/text{out}_i}/P_{/text{in}})/).

· Numerical Characteristics:

· Influence of Splitting Ratio: The more the number of splits, the higher the loss. For example, a 1×2 splitter typically has a loss of about 3.7dB, while a 1×64 splitter can reach 19.5dB.

· Process Differences: The loss of a fused biconical taper (FBT) 1×2 splitter is about 3.4dB, and the average loss of a planar lightwave circuit (PLC) 1×64 splitter is 16.6dB.

· Engineering Calculation: In an ODN network, power budgeting must consider fiber loss (0.35dB/km), connector loss (0.1-0.3dB), and optical margin (1dB). For example, when a 1×32 splitter is used for 20km transmission, the total loss must be controlled within 28dB.

2. Additional Loss

· Definition: The difference between the total power of all output ends and the power of the input end, reflecting manufacturing process defects.

· Typical Values:

· For a 1×2 splitter, it is ≤0.2dB, and for a 1×16 splitter, it is ≤1.2dB.

· The additional loss of FBT type is lower than that of PLC type; for example, the additional loss of a 1×2 FBT splitter is ≤0.1dB.

· Influencing Factors: Fiber fusion accuracy, waveguide chip defects, etc., directly affect the long-term stability of the system.

3. Splitting Ratio

· Classification:

· Uniform Splitting: PLC type is mostly 50:50, and FBT type can be customized with unequal ratios (such as 10:90).

· Wavelength Sensitivity: The splitting ratio of the same splitter at 1310nm and 1550nm wavelengths may vary significantly (e.g., from 50:50 to 70:30).

· Application Case: In an FTTH network, a 1×64 splitter supports 32 households to share bandwidth, with a single-user peak bandwidth of approximately 156Mbps (50% concurrency rate).

4. Return Loss

· Definition: The ratio of reflected light power to incident light power. High return loss can reduce signal interference.

· Standard Requirements:

· APC interface ≥55dB, UPC interface ≥50dB.

· The return loss of PLC splitters is generally better than that of FBT splitters, making them suitable for high-speed data transmission scenarios.

5. Polarization-Dependent Loss (PDL)

· Definition: The fluctuation of insertion loss caused by changes in the polarization state of the optical signal, in dB.

· Performance Comparison:

· FBT type PDL ≤0.15dB, PLC type ≤0.2dB.

· Low PDL is crucial for coherent optical communication systems (such as 100G PON) to avoid the impact of polarization mode dispersion (PMD).

II. Key Physical Properties and Environmental Adaptability

1. Loss Uniformity

· Definition: The maximum difference in insertion loss between output ports.

· Typical Values:

· 1×2 PLC type ≤0.4dB, 1×64 type ≤2.5dB.

· The uniformity of FBT type is poor, and the difference of 1×8 splitters can reach 1.5dB.

· Application Impact: In PON systems, uniformity directly affects the consistency of signal quality among multiple users.

2. Wavelength-Dependent Loss (WDL)

· Definition: The degree to which insertion loss changes with wavelength, in dB/nm.

· Process Differences:

· PLC type WDL ≤0.8dB (1×64), FBT type has high WDL due to the sensitivity of the fusion process to wavelength.

· Applicable Scenarios: Triple-play (voice, data, video) requires wide wavelength support (1260-1650nm), and PLC type has more advantages.

3. Temperature-Dependent Loss (TDL)

· Definition: The fluctuation of insertion loss caused by temperature changes, in dB/℃.

· Performance Indicators:

· In the range of -40℃~85℃, the TDL of 1×2 PLC type is ≤0.5dB, and that of 1×64 type is ≤1.0dB.

· Due to the difference in thermal expansion coefficients of materials, the TDL of FBT type is usually higher than that of PLC type.

· Engineering Response: A 3dB optical power margin should be reserved for outdoor deployment to cope with fiber aging and temperature fluctuations.

4. Directivity

· Definition: The degree of light leakage from non-output ports, in dB.

· Standard Requirements: ≥55dB. High directivity can reduce crosstalk and is suitable for dense wavelength division multiplexing (DWDM) systems.

III. Manufacturing Processes and Parameter Correlation

1. Fused Biconical Taper (FBT)

· Process Characteristics:

· Splitting is achieved by high-temperature melting and stretching of fibers, with low cost but poor uniformity.

· Supports unequal splitting (such as 5%:95%), but has significant wavelength sensitivity.

· Parameter Limitations:

· The insertion loss uniformity difference of 1×8 splitters can reach 1.5dB, and the temperature stability is poor.

· Application Scenarios: Suitable for low-cost, low-order splitting (below 1×8), such as independent data transmission or CATV networks.

2. Planar Lightwave Circuit (PLC)

· Process Characteristics:

· Waveguides are integrated on a silicon-based chip using lithography technology, with high splitting uniformity (±1%).

· Supports high-order splitting (1×64) and a wide wavelength range (1260-1650nm).

· Parameter Advantages:

· Polarization-dependent loss (PDL) ≤0.2dB, with excellent temperature stability.

· Application Scenarios: FTTH, 5G fronthaul networks and other scenarios requiring high reliability and wide wavelength support.

3. Other Types

· Micro-Electro-Mechanical System (MEMS): Realizes dynamic splitting through micro-mirror arrays, suitable for tunable optical networks but with high cost.

· Silicon Photonics PLC: Manufactured using CMOS technology, can integrate more functions (such as filters), and is expected to further reduce costs in the future.

IV. Mechanical and Environmental Parameters

1. Port Types and Packaging

· Interface Types:

· SC/APC (anti-reflection) is used for CATV, LC for high-density data centers, and FC for high mechanical stability scenarios.

· Packaging Forms:

· Box type (100×80×10mm) is suitable for outdoor optical cable cross-connect cabinets, and 19-inch rack-mounted type supports centralized management.

· Pluggable design (as described in summary 9) supports high-density installation, and the handle ring and locking spring simplify maintenance.

2. Size and Weight

· Typical Values:

· A 1×64 PLC splitter has a size of approximately 60×12×4mm and a weight of ≤50g.

· The FBT 1×8 splitter has a larger volume (100×80×10mm) due to the need to protect the fused taper area.

3. Environmental Reliability

· Testing Standards:

· Must pass Telcordia GR-1209/1221 certification, including temperature cycling (-40℃~85℃), humidity (85% RH), vibration (5-500Hz) and other tests.

· The fused biconical taper type is stable in the range of -20℃~70℃, and the PLC type is extended to -40℃~85℃.

V. Application Scenarios and Parameter Selection

1. Fiber to the Home (FTTH)

· Key Parameters:

· High-order splitting (1×64) requires insertion loss ≤17dB and temperature fluctuation <0.5dB.

· Choose PLC type to ensure uniformity (±1% splitting ratio) and long-term stability.

2. Data Centers

· Key Parameters:

· Low return loss (≥55dB) and high directivity (≥55dB) to reduce the interference of light reflection on high-speed signals.

· LC interface supports high-density wiring, and pluggable packaging is convenient for maintenance.

3. 5G Fronthaul Networks

· Key Parameters:

· Supports 25G/50G rates, PDL ≤0.2dB to avoid polarization mode dispersion.

· Single-fiber bidirectional (BiDi) splitters reduce fiber usage and require wavelength isolation ≥30dB.

4. Cable Television (CATV)

· Key Parameters:

· High return loss (APC interface ≥55dB) and wide wavelength support (1550nm) to reduce signal reflection and crosstalk.

· FBT type is widely used due to its low cost and strong wavelength targeting (such as 1550nm).

VI. Industry Standards and Testing Methods

1. International Standards

· Telcordia GR-1209: Defines performance indicators, including insertion loss (≤4.0dB for 1×2), return loss (≥50dB), etc.

· Telcordia GR-1221: Specifies reliability tests, such as temperature cycling (-40℃~85℃, 100 times), mechanical shock (50g), etc.

2. Testing Methods

· Insertion Loss Test: Use an optical power meter to compare input and output power, which needs to be verified at multiple wavelengths such as 1310nm, 1490nm, and 1550nm.

· PDL Test: Change the polarization state of the optical signal through a polarization controller and measure the loss fluctuation range.

· Uniformity Test: Measure the insertion loss port by port and calculate the difference between the maximum and minimum values.

VII. Future Development Trends

1. Silicon Photonics Integration: PLC splitters based on CMOS technology will integrate more functions (such as tunable filters) to reduce costs and improve performance.

2. Dynamic Splitting Technology: MEMS or thermo-optically tunable PLC splitters will support flexible optical network configuration to meet the dynamic bandwidth requirements of 5G and cloud computing.

3. Green Energy-Saving Design: The use of low-power packaging materials (such as ceramics) reduces heat dissipation requirements for outdoor deployment.

Summary

The parameter characteristics of optical fiber splitters need to be comprehensively considered from optical performance, environmental adaptability, manufacturing processes, and application scenarios. PLC type has become the mainstream due to its high uniformity, wide wavelength support, and stability, while FBT type still has advantages in low-cost and unequal splitting scenarios. With the popularization of 5G and FTTH, splitters will develop towards higher order, lower loss, and intelligence, while meeting more stringent industry standards (such as Telcordia GR-1209/1221). In engineering design, parameter combinations need to be optimized according to specific scenarios (such as transmission distance, bandwidth requirements) to ensure the reliability and economy of the optical network.