How to Select a Pump Combiner
Short answer: Pick the architecture first: an N×1 combiner merges pump fibers only, while an (N+1)×1 pump and signal combiner adds a central signal fiber (PM if polarization matters) for MOPA amplifier stages. Then match three interfaces as one chain — pump fibers to the diode pigtails, signal fiber to the seed/gain fiber, and the double-clad output to the active fiber — and check brightness: Dpump·NApump·√N ≤ Dclad,out·NAclad,out.
Combiner compatibility depends on the complete optical chain: port configuration, fiber core/cladding geometry, numerical aperture, signal alignment and thermal conditions. Engineering review can begin with the application and available fiber information.
Quick comparison
| Need | N×1 (063) | (2+1)×1 PM (064) | (6+1)×1 PM (065) |
|---|---|---|---|
| Signal path through combiner | No | Yes, PM Panda (slow axis) | Yes, PM Panda |
| Pump ports | 3×1 or 7×1 | 1 or 2 | 6 |
| Pump wavelength | 800–1000 nm | 800–1000 nm | 800–1000 nm |
| Signal wavelength | — | 1030–1080 or 1450–1600 nm | 1030–1080 or 1450–1600 nm |
| Pump efficiency | >95% | >90% (X/125), >93% (X/250), >95% (20/400) | >90%, >93%, >95% |
| Max power per pump | 200 W | ≤50 W (X/125), ≤100 W (X/250), ≤200 W (20/400) | ≤50, ≤100, ≤200 W |
| Signal IL / PER | — | ≤0.5 dB / ≥18 dB | ≤0.7 dB (typ. 0.5) / ≥18 dB |
| Typical use | Pump-only combining, end-pumped oscillators | Preamplifier / intermediate stage | Main power amplifier stage |
Values from the 063/064/065 datasheets. Final configuration is confirmed by engineering review.
Selection logic
Quick answer
An N×1 Pump Combiner combines multiple pump inputs into one output fiber without a separate signal input. A (6+1)×1 architecture combines six pump inputs and one signal input into a common output. Port count is only the first filter; fiber mapping, NA, wavelength, power and package must be reviewed together. See the N×1 Pump Combiner and (6+1)×1 PM Pump and Signal Combiner. Final configuration is subject to engineering confirmation.
1. Combiner topology: N×1 and (N+1)×1
N×1 Multi-Mode Pump Combiners (Model 063) combine multiple diode pumps into a single double-clad output fiber without a central signal core. Designed for end-pumped fiber laser oscillators and direct-diode beam delivery. Standard port counts include 3×1, 4×1, and 7×1.
(N+1)×1 Pump and Signal Combiners (Model 064, Model 065) are used in master oscillator power amplifier (MOPA) systems. A central single-mode or PM signal fiber guides the seed signal while 2 to 6 multi-mode pump ports inject high pump power into the active fiber cladding. Standard configurations include (1+1)×1, (2+1)×1, and (6+1)×1.
2. Optical brightness conservation
In all fused biconical taper (FBT) combiners, optical radiance cannot be increased. To avoid unguided pump light leaking into the low-index outer fluoro-polymer coating (which creates thermal hotspots and destroys recoating), the aggregate numerical aperture and area invariant must strictly satisfy the brightness criterion:
Dpump_core · NApump · √N ≤ Dclad_out · NAclad_out
Illustrative calculation only: apply the brightness condition to the actual input fibers, output fiber and optical condition. The calculation does not replace an approved product specification or engineering review.
3. Signal fiber compatibility & polarization extinction
For polarization-maintaining (PM) fiber lasers, preserving the polarization extinction ratio (PER ≥ 18–20 dB) is vital. Symmetrical (2+1)×1 architectures minimize lateral stress on Panda stress rods for pre-amplifier stages. For high-power booster stages, (6+1)×1 hexagonal packing maximizes pump delivery into 20/400 or 25/250 active fibers.
Package and cooling review
Specify the selected fiber configuration, power per pump port, mounting space and cooling available. Package choice and thermal requirements are confirmed during engineering review; package codes alone do not establish a total power rating.
Send: port configuration · pump and signal wavelength · pump fiber core/cladding/NA · signal fiber (PM or not) · output/active fiber · power per pump port and total · package, pigtail, quantity. Unknown items can be left blank for engineering review. Samples are paid; typical lead time 4–10 weeks.
PM Pump & Signal Combiner Fiber-Matching Worksheet (Printable)
Reviewed by Erica Zhong, CEO, KernsOptic · KernsOptic · Updated October 13, 2026
Short answer: A PM pump and signal combiner works only when all three interfaces are matched as one optical chain: (1) pump input fibers to your pump-diode pigtails, (2) the PM signal fiber to your seed or gain fiber, and (3) the double-clad output fiber to your active fiber. Fill in the three tables below, run the brightness check, and leave anything you don't know blank — engineering review will check it with you.
Print this page (A4/Letter) or copy the tables into your RFQ. Blank fields are fine: this worksheet helps you describe the requirement; it is not a gate.
How to use this worksheet
- Decide the architecture (Section 1).
- Fill one row per interface (Sections 2–4).
- Run the brightness check (Section 5).
- Tick the pre-RFQ checklist (Section 6) and send it with your request at Request a Quote.
1. Architecture
| Question | Your answer |
|---|---|
| Pump-only (N×1) or pump + signal ((N+1)×1)? | ☐ N×1 ☐ (1+1)×1 ☐ (2+1)×1 ☐ (6+1)×1 ☐ Other: ____ |
| Forward or backward (counter-) pumping? | ☐ Forward ☐ Backward ☐ Not sure |
| Amplifier stage | ☐ Preamplifier / intermediate ☐ Main power amplifier ☐ Oscillator ☐ Other |
| Must the signal path be PM? | ☐ Yes (PM Panda) ☐ No ☐ Not sure |
Reference ranges from KernsOptic datasheets 063/064/065:
| Item | N×1 (063) | (2+1)×1 PM (064) | (6+1)×1 PM (065) |
|---|---|---|---|
| Port configuration | 3×1, 7×1 | (1+1)×1 or (2+1)×1 | (6+1)×1 |
| Pump wavelength | 800–1000 nm | 800–1000 nm | 800–1000 nm |
| Signal wavelength | — | 1030–1080 or 1450–1600 nm | 1030–1080 or 1450–1600 nm |
| Pump efficiency | >95% | >90% (X/125), >93% (X/250), >95% (20/400) | >90% / >93% / >95% |
| Max. power per pump | 200 W | ≤50 W / ≤100 W / ≤200 W | ≤50 W / ≤100 W / ≤200 W |
| Signal insertion loss | — | ≤0.5 dB | ≤0.7 dB (typ. 0.5) |
| PER (PM fiber type) | — | ≥18 dB | ≥18 dB |
| Return loss | — | >45 dB | >45 dB |
| Operating temperature | −5 to +70 °C | −5 to +70 °C | −5 to +70 °C |
| Package | D1–D7 or custom | D1, D3; others per engineering | D6, D7 or customized (dimensions confirmed in engineering review) |
Values from KernsOptic datasheets 063, 064, 065. Final configuration is subject to engineering review.
2. Interface A — Pump input fibers
| Field | Port 1 | Port 2 | Port 3 | Port 4 | Port 5 | Port 6 |
|---|---|---|---|---|---|---|
| Diode pigtail fiber model | ||||||
| Core / cladding (µm) — e.g. 105/125 or 200/220 | ||||||
| NA — e.g. 0.22 | ||||||
| Pump wavelength (nm) | ||||||
| Power per port (W) | ||||||
| Splice or connector |
Unused ports: ____ (tell us; the output fiber and power budget are reviewed for the real configuration.)
3. Interface B — Signal fiber (center port)
| Field | Your value |
|---|---|
| Seed / upstream fiber model | |
| Core / cladding (µm) — X/125, X/250, 20/400… | |
| PM type (Panda / other / non-PM) | |
| Polarization axis to align (slow / fast) | |
| Mode field diameter (µm) | |
| Signal wavelength (nm) | |
| Signal power (W, CW or peak) | |
| Required PER at output (dB) | |
| Allowed signal insertion loss (dB) |
4. Interface C — Double-clad output fiber
| Field | Your value |
|---|---|
| Active / downstream fiber model | |
| Core / inner cladding (µm) — Y/125, Y/250, 20/400… | |
| Core NA | |
| Inner-cladding NA | |
| PM type | |
| Total pump power through output (W) | |
| Cooling available (passive plate / water / unknown) | |
| Package or length constraints |
5. Brightness check
Rule of thumb: pump light should stay guided in the output inner cladding if:
D_pump × NA_pump × √N ≤ D_clad,out × NA_clad,out
The √N form is a simplified estimate (it assumes identical, closely packed pump fibers and ignores taper losses). Use it as a first screen; engineering review confirms the actual design.
| Term | Value |
|---|---|
| D_pump (pump fiber core, µm) | |
| NA_pump | |
| N (number of pump ports) | |
| Left side = D_pump × NA_pump × √N | |
| D_clad,out (output inner cladding, µm) | |
| NA_clad,out | |
| Right side = D_clad,out × NA_clad,out | |
| Pass? | ☐ Left ≤ Right ☐ Fails — ask engineering |
Worked example (arithmetic only, not a product guarantee): 6 pumps of 105 µm / 0.22 NA → 105 × 0.22 × √6 ≈ 56.6. Output inner cladding 400 µm at NA 0.46 (illustrative value) → 400 × 0.46 = 184. Left ≤ Right, so the condition is met. Use your own fibers' NA values from their datasheets.
If the condition fails, pump light can leak into the low-index coating and create hotspots.
6. Configuration review notes
- ☐ Architecture and port count chosen
- ☐ Pump fiber core/cladding/NA for every port
- ☐ Signal fiber type, PM or not, axis
- ☐ Output/active fiber core, inner cladding, NAs
- ☐ Wavelengths (pump and signal)
- ☐ Power per pump port and total; signal power
- ☐ Brightness check done (or marked "please check")
- ☐ Package, cooling and pigtail length constraints
- ☐ Quantity (prototype / pilot / volume)
- ☐ Acceptance tests you need reported
Commercial notes: prototypes and samples are paid; typical build lead time is 4–10 weeks. Pricing and feasibility are confirmed by KernsOptic engineering.
FAQ
Do I need to fill in every field before requesting a quote?
No. Fill in what you know. Blank fields are clarified during engineering review.
Which fibers have to match in a pump and signal combiner?
All three interfaces: pump inputs to the diode pigtails, the signal fiber to the seed or gain fiber, and the double-clad output to the active fiber's core and inner cladding.
What PER can a PM pump and signal combiner keep?
KernsOptic models 064 and 065 are specified at PER ≥18 dB (PM fiber type).
How much pump power per port is possible?
Per datasheets 064/065: ≤50 W with X/125, ≤100 W with X/250, ≤200 W with 20/400 fiber. Other configurations are reviewed by engineering.
Can you build with a customer-specified fiber?
Custom fiber, port geometry and acceptance requirements are reviewed case by case. Send your fiber data, application and quantity.
| Anchor text | Target |
|---|---|
| how to select a PM pump and signal combiner | /guides/how-to-select-pump-combiner |
| Nx1 vs (6+1)x1 pump combiner | /guides/nx1-vs-6plus1x1-pump-combiner |
| (2+1)x1 vs (6+1)x1 PM combiner | /guides/2plus1x1-vs-6plus1x1-pm-pump-signal-combiner |
| Nx1 pump combiner | /products/exact/063-nx1-pump-combiner |
| (2+1)x1 PM pump and signal combiner | /products/exact/064-2-plus-1-x1-pm-pump-and-signal-combiner |
| (6+1)x1 PM pump and signal combiner | /products/exact/065-6-plus-1-x1-pm-pump-and-signal-combiner |
| send your fiber data for engineering review | Request a Quote |
Frequently asked questions
What is the difference between an N×1 and an (N+1)×1 pump combiner?
An N×1 combiner merges several multimode pump fibers into one output fiber and has no signal path. An (N+1)×1 pump and signal combiner adds a central signal fiber, so the seed signal and the pump light share a double-clad output, as used in MOPA amplifier stages.
Which fibers must be matched in a pump and signal combiner?
All three interfaces: the pump input fibers to the pump-diode pigtails, the signal fiber to the seed or gain fiber, and the double-clad output fiber to the active fiber's core and inner cladding. They should be reviewed as one optical chain.
How do I check that the pump light will stay guided?
Apply the brightness condition D_pump·NA_pump·√N ≤ D_clad,out·NA_clad,out to your actual pump and output fibers. If it is not met, pump light can leak into the low-index coating and create hotspots.
What should I send for a custom pump combiner quote?
Port configuration, wavelengths, pump/signal/output fiber data, power per port and total, and package constraints. Missing items can be clarified in engineering review. Samples are paid and typical lead time is 4–10 weeks.